The Tories are known for ruthlessly ditching leaders – Boris Johnson will be looking over his shoulder

“Boris doesn’t really believe anything except people like him should be left alone to do what they want,” one former Boris Johnson aide told me. Indeed, Johnson has reportedly earned more than £4m from his outside interests in the past 14 years.

Perhaps this helps to explain his woeful mishandling of the Owen Paterson affair and his reluctance to tighten the MPs’ code of conduct. On Monday, the Commons will formally overturn the ill-fated decision to change the system of investigating complaints against MPs to try to save Paterson’s skin. Johnson should use this opportunity to apologise for the fiasco and to support moves to restrict MPs’ second jobs – including a ban on acting as parliamentary consultants.

But he probably won’t. Cabinet ministers including Rishi Sunak, Steve Barclay and Nadhim Zahawi have been much more contrite than Johnson; it is not in his DNA to say sorry. This is compounding the damage to him and his party from a controversy that was his own making.

Only a month after seeming all-powerful at the Tory conference, Johnson’s standing among Tory MPs has sunk to its lowest level. The public, and the new generation of Tory MPs in the Midlands and the north, want tougher rules on MPs’ conduct. But Johnson doesn’t want to alienate a band of ex-ministers who want to keep their second jobs after losing their ministerial salaries. This awkward squad could make life very difficult for him.

Johnson seems to be in denial. The journalist in him believes the media storm will blow itself out, but it has been on the front pages for nine days and shows little sign of abating. Nadine Dorries, the culture secretary, told Tory MPs on WhatsApp that the 2009 scandal over MPs’ expenses was “a billion times worse”. She conveniently forgot that Labour was in power then and opposition leader David Cameron deflected anger over Tory MPs’ expenses by proposing measures to clean up politics. (Whatever happened to him?)

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Today, the return of “Tory sleaze” has helped Labour draw level in the opinion polls. Johnson’s position among his MPs will worsen if they no longer think he’s a winner. He knows his party ruthlessly ditches leaders when it believes they will lose – as Margaret Thatcher, Iain Duncan Smith and Theresa May discovered. As one senior Tory said crudely: “Boris is there because he is an asset. If he is seen a liability, the game will be up.” His own support among his MPs has always been shallow, leaving him vulnerable to a sudden and dramatic loss of support.

We are not at that point yet. But sooner or later, Johnson will need action rather than words to reassure the public he will tighten and uphold the rules. Instead of undermining regulators, he should put parliament’s standards commissioner and advisers on the ministerial code and business appointments on a statutory footing. Crucially, he should accept their rulings rather than ignore them.

It is remarkable that when Priti Patel was found to have broken the ministerial code after allegedly bullying Home Office officials, she remained in post while the ministerial adviser Alex Allan resigned. (This story is not over yet: a judicial review of Johnson’s decision will be heard on 17 November.)

The most significant episode in the current controversy came when Kwasi Kwarteng, the business secretary, suggested Kathryn Stone, the parliamentary standards’ watchdog, consider her position. That gave the game away. As I reported in April, Johnson feared Stone would investigate how he funded the refurbishment of his Downing Street flat, and she regarded him as “disrespectful” of the rules on MPs’ registering their interests. The backcloth to the “save Paterson” move was a belief among Tories that Stone is biased against them; her critics’ favourite example is her harrying MPs, including the then culture minister, Caroline Dineage, for not registering a trip to the Brit awards.

For me, Stone is doing the job parliament asked her to do, without fear or favour. But the strong feelings about her contributed to Johnson’s foolish attempt to rescue Paterson. The can of worms he opened exposed flaws in the rules on MPs’ second jobs which have allowed Geoffrey Cox, the former attorney general, to earn about £6m as a lawyer since becoming an MP in 2005.

The committee on standards in public life, set up by John Major after the original “Tory sleaze” scandal, has rightly been calling for tighter controls on MPs’ second jobs since the expenses row. In 2018, it proposed: “MPs should not accept any paid work to provide services as a parliamentary strategist, adviser or consultant.” The committee rejected a time or earnings limit on outside work but proposed it should not prevent them fully undertaking their primary role as an MP, with possible breaches investigated by the standards commissioner.

In order to end this sorry saga, Johnson should come out for curbs on second jobs – short of the total ban that would prevent MPs working as doctors and nurses and might deter high calibre people from entering parliament. Much better for Johnson to act quickly now than grudgingly later. And say sorry for the mess he created.