Spies like us: New films by David Hare and John le Carré show human side of the intelligence services

British spooks are back on screen. Next month sees the release of Working Title's feature-film version of the John le Carré novel Tinker Tailor Soldier Spy, with Gary Oldman as the MI6 officer George Smiley and Colin Firth as fellow spy Bill Haydon. Meanwhile, David Hare's first film as a director in two decades, the thriller Page Eight, will be shown on Sunday on BBC2.

Both films concentrate on the enemy within. One unfolds during the Cold War, the other during the ongoing fight against international terror, but both are as much about something rotten in the state of Britain as about external threats.

In Tinker Tailor Soldier Spy, which is set in the 1970s and directed by Tomas Alfredson, Smiley's quest is to flush out a Moscow Centre "mole" who has been operating within the heart of British intelligence for over three decades.

The key charge in Page Eight is that a British Prime Minister (Ralph Fiennes) has hidden secrets from his own security services. As the long-serving MI5 officer Johnny Worricker (Bill Nighy) discovers, when an incriminating dossier falls into his hands, the Prime Minister had access to intelligence about potential British terrorists that might have saved British lives, and yet "he didn't tell anyone".

To viewers who remember Alec Guinness's celebrated performance as Smiley in the 1979 TV series of Tinker Tailor Soldier Spy, the new film may seem like an impostor. Smiley, as described by le Carré and so brilliantly embodied by Guinness, is "small, podgy, at best middle-aged", a penguin-like figure with short legs and an ungainly gait who wears a black overcoat. That is a long way removed from the roles for which Oldman (who made his reputation playing livewire characters like Sid Vicious and Joe Orton) is known.

Tinker Tailor Soldier Spy is also a departure for Working Title, which has enjoyed its most notable successes with the Bridget Jones films and Richard Curtis comedies. Whenever Working Title has strayed too far from middle England – as, for example, it did with Paul Greengrass's Iraq thriller Green Zone – box-office takings have plummeted. Nonetheless, the new Tinker Tailor has received le Carré's enthusiastic blessing.

The veteran author said: "The film, through my very personal prism, is a triumph. And if people write to me and say, 'How could you let this happen to poor Alec Guinness,' I shall reply that, if 'poor Alec' had witnessed Oldman's performance, he would have been the first to give it a standing ovation. It's not the film of the book. It's the film of the film, and to my eye a work of art in its own right. I'm very proud to have provided Alfredson with the material, but what he made of it is wonderfully his own."

Page Eight, befitting its subject matter, is a slippery and deceptive affair. Its characters may be drawn from the present day but they are not so different from the types who inhabit le Carre's Smiley novels: spies from public-school backgrounds who are well into middle age. On the one hand, Hare's film is a ripping yarn with a top-notch cast (Nighy, Michael Gambon, Judy Davis, Rachel Weisz, etc) and a hint of John Buchan and Ian Fleming, as well as of le Carré, about it. On the other, it is an intensely political drama, raking over how intelligence gathering has been utterly corrupted in the war on terror and arguing that moral boundaries have blurred as a result.

As one of Hare's characters complains: "There's so much intelligence, ceaseless intelligence, and there's so little time to consider it." When revelations of real value are unearthed, analysts are so swamped with other data that they either don't notice or don't take it seriously.

Page Eight suggests that the reason the Prime Minister kept the intelligence to himself is because of his slavish loyalty to his US allies. Hare is back on familiar turf. He and other writers and film-makers have been this way many times since the beginning of the war in Iraq. Americans (we hear again) have "prisoners all over the world who don't officially exist, on black sites, unknown sites". Information gleaned from these prisoners isn't shared fully with the British security forces. Nor is the fact that it has been obtained by torture. The Americans have been lying to MI5 and MI6 but so, in order to protect his allies, has the Prime Minister. That is what is at the bottom of page eight of the dossier: "Downing Street already knows about this."

The world Page Eight depicts is clearly fictional. The aggressive, close-cropped Prime Minister played by Fiennes bears little resemblance to Tony Blair or Gordon Brown. Bill Nighy's Waitrose bag-wielding MI5 officer may not be Daniel Craig material but he has a bit more spy-movie dash about him than Smiley does. An art-loving jazz aficionado, coming towards retirement, Worricker does not leap from rooftops, have fistfights with thugs or drive an Aston Martin. (He has a Saab.) Nonetheless, he is adept at spycraft: picking locks, photographing secret documents and losing the Special Branch officers sent to tail him. As attested by his many marriages and relationships, women like him too. Nighy excels as the sardonic but incorruptible hero, trying to outdo his boss and best friend Benedict Baron (Gambon) in sarcasm and deadpan humour.

Hare throws in plenty of stock thriller characters. Ewen Bremner plays a hardboiled journalist with close connections to the intelligence services. Weisz is an improbably glamorous peace campaigner who lives across the landing from Nighy, grieving the death of her peace-activist brother in the Middle East, at the hands of the Israelis. There are tremendous cameos from Saskia Reeves, as a tough-as-nails Home Secretary, and Judy Davis, in Cruella de Vil mode as a ruthless intelligence boss.

Despite his adherence to familiar spy-film conventions, Hare has offered tantalising hints that much of Page Eight is based on real events. Like the main characters in the film, he won't disclose his sources. However, he has claimed to have been briefed about what has been going on in Britain's "spook" community in the last decade.

"I know a little about what's been going on inside MI5 in the last 10 years," he said in an interview, earlier this summer. "Plainly, in the run-up to the Iraq war the intelligence agencies were being asked to come up with evidence which suited the Government's case. To its credit MI5, if I believe what I am told, refused to do that, whereas MI6 went along with it and came up with all the stuff that went into the dodgy dossiers."

In both Tinker Tailor Soldier Spy and Page Eight, the security forces are portrayed as expending much of their energy on spying on one another.

Audience demand for homegrown British spy stories does not show any sign of abating. The MI5-themed drama Spooks (into its 10th and final series) has been one of the BBC's most popular dramas in recent years. "So good it makes you want to be a spy," one critic enthused. The 23rd Bond film will be out on 26 October next year.

The spy genre is pulling in two directions. On the one hand there are muscular action dramas, starring the likes of Daniel Craig and Matt Damon. On the other there are spy movies like Tinker Tailor and Page Eight, playing up the human factor. Such films may seem to be about weighty political matters and ideological battles but their drama really hinges on personal relationships, whether between colleagues or between husbands and wives and parents and children. These films are about trust and deceptions. The bigger betrayals are always mirrored in the domestic sphere. Look, for example, at the constant references to the adultery committed by Smiley's wife in Tinker Tailor Soldier Spy.

This is something that Hare makes clear in Page Eight, too. Nighy's MI5 officer may have fraught relationships with politicians and bosses but they are nothing like as complex as those he has with his ex-wife or his daughter. The daughter (Felicity Jones) is an artist who paints graphic and harrowing images of Guantanamo Bay-like torture victims. (Ironically, some of her work has found its way into the Government's art collection. One of her paintings hangs in the MI5 boardroom.) Father and daughter misinterpret one another's motives and fail (at least initially) to decode each other's feelings.

This human factor is what makes the spy genre so compelling and so durable. The Lives Of Others (2007), perhaps the best character-based spy film of recent times, hinges on the fact that the eavesdropping Stasi security captain feels an emotional bond with the playwright he is snooping on that transcends his political beliefs and his rigid sense of duty.

However, the human factor is also arguably what makes the spy movie ultimately unsatisfactory as a vehicle for polemic or whistleblowing. If Hare was hoping to draw attention in Page Eight to the misdeeds of British politicians or senior spooks, he hasn't really succeeded. The relationships and the adventure get in the way of the politics. In the end, as viewers, we're more interested in whether Nighy will escape from the heavies pursuing him in the multi-storey car park than we are in the way that the Prime Minister has misled his own security forces.

Hare delivers an enjoyable, well-crafted thriller along traditional lines. Whether there is anything in Page Eight that might have been of interest to the Chilcot Inquiry is another matter. As for Tinker Tailor Soldier Spy, audiences are likely to be so busy comparing Oldman with Alec Guinness and trying to work out the identity of the "mole" that they will not be overly concerned with any points the film-makers are trying to make about corruption and treachery at the heart of the British State.

'Page Eight' will screen on Sunday at 9pm on BBC2. 'Tinker Tailor Soldier Spy' is released in cinemas on 16 September