And now, the Michael Balcon award for the most bitter cinema feud goes to...

The simmering feud started 25 years ago with a seemingly innocuous letter sent by Richard Attenborough, the actor and director, to the family of Sir Michael Balcon, one of the greatest producers in British cinema history.

It ended with a ban on Lord Attenborough and other cinema luminaries ever again being allowed access to Sir Michael's remarkable collection of papers and film memorabilia, held by the British Film Institute (BFI).

The bitter dispute turns on a subtle change of wording to a prestigious film award won by, among others, Lord Puttnam, the Monty Python team, Kenneth Branagh, Derek Jarman, Ridley and Tony Scott, Ken Loach and Mike Leigh.

Sir Michael was a key figure in British cinema history. He launched Alfred Hitchcock's career and was the power behind Ealing studios in its heyday. He produced such great films as Kind Hearts and Coronets and Whisky Galore. He also founded Bafta, the British Academy of Film and Television Arts, in 1947, which makes the ban on access to the archive, made public by his son Jonathan last week, all the more hurtful.

In an email seen by The Independent on Sunday, Jonathan Balcon, a former Lloyd's broker, wrote to Simon Relph, Bafta's present chairman, on 18 May informing him: "Instructions are being given to the BFI that NO Member of Bafta (Individual or Corporate) is to have access to the Balcon Papers in perpetuity. After my demise this will be enforced by one of my three daughters." That email was one of a string sent by Jonathan, who admits to being "disgusted of Tunbridge Wells", where he now lives.

Mr Balcon has a record of falling out with people, notably his own sister Jill, who married the poet laureate Cecil Day-Lewis. The siblings no longer talk – and neither does Mr Balcon talk to his nephew Daniel Day-Lewis, the Oscar-winning actor.

When Day-Lewis was invited to unveil a plaque in memory of his grandfather at Sir Michael's home, Jonathan made it clear he wanted his nephew to stay away. In a letter to organisers he wrote his father "would have been horrified by his sexual mores and total lack of feeling towards the various women he has bedded and by one of whom he has an illegitimate child".

Other emails to Bafta have been more noxious. On 17 May, Jonathan wrote: "You and your Bafta are the most convoluted people. Far from being Democratic I would say that you verged on being Fascist," before concluding: "I hope Mick [Sir Michael Balcon] curses you all from the grave, I certainly will." And: "I am a bad enemy to have."

The dispute began in 1978, a year after Sir Michael's death, when Lord Attenborough, president of Bafta, wrote a letter to his widow informing her of the desire to name a Bafta award in honour of her husband.

Things get murky after that but Jonathan, now aged 70, insists Lord Attenborough promised a Sir Michael Balcon award for Outstanding Contribution to British Cinema but what they ended up with was an award for Outstanding British Contribution to Cinema. The alleged change of words is a subtle one but that and other matters – such as award winners and givers he has disapproved of and the alleged failure to consult on recipients – has infuriated Jonathan Balcon.

"They suddenly changed the terms of reference and it became an outstanding British contribution to cinema. That is very, very different. It is moving the goalposts. I found it very hurtful. They don't even bother to consult me on who the award winners are.

"It has been ongoing with Bafta since 1978. But each time I have corresponded they have ignored me. Or I have had a letter back saying 'Eff off'."

His father, he says, was devoted to British cinema but an award for British achievements in Hollywood is against his wishes.

In an email sent by Simon Relph to Mr Balcon, he says: "Your three emails are so discourteous to me and the Academy, which you clearly despise, as to make me think once again that there really is no purpose in our continuing this correspondence.

"Clearly, you have held a grievance against the Academy for very many years and there is nothing I can do, short of agreeing not to continue with an award named after your father, or allowing you to be personally involved in the selection of the Award winners, which will satisfy you. This is not in my power to agree to, but I will copy this correspondence to my colleagues on Council and discuss it with them. I will get back to you when I have done that."

Neither Mr Relph nor Lord Attenborough were available for comment but Bafta issued a statement saying: "The academy wanted to honour the contribution Michael Balcon made to film and we hold this award in the highest esteem."