MPs have backed a move that could curb their ability to take other jobs, as Boris Johnson sought to neutralise criticism that he had been soft on backbenchers’ outside interests. Keir Starmer had planned to use an opposition-led debate in parliament to table a motion suggesting MPs be banned from taking any paid work as a parliamentary strategist, adviser or consultant. But Johnson wanted to look as if he was going further than the Labour leader. He proposed an amendment that said MPs who prioritise other paid roles over serving their constituents should also be investigated and “appropriately punished”. However, there was frustration that it said nothing about how it would be determined if an MP was spending too much time doing another job and was branded a “wrecking amendment” by Labour. Labour’s initial motion was defeated by 231 votes to 282, but it and other opposition parties did not oppose the government’s amendment, meaning it passed by 297 votes to 0. It means the standards committee, which reviews the MPs’ code of conduct, will need to consider the result and announce recommendations to update the code by next February. The vote comes after weeks of scrutiny on MPs’ outside financial interests, including Owen Paterson’s “egregious” breach of lobbying rules and the revelation that Geoffrey Cox had collected nearly £6m from legal work, appeared to use his Commons office to attend a virtual hearing, and voted by proxy from the British Virgin Islands. Despite the result on Wednesday night, many MPs – including some Conservatives – felt it was a pointless exercise, given the standards committee is already reviewing the code. The committee’s chair, Chris Bryant, said people were trying to bounce it in to doing something it was already in the process of, and acting like “headless chickens”. He said: “The committee has been engaged in an evidence based review of the code of conduct for more than a year and is close to completing its work which we hope to do before Christmas or even before the end of the month.” Bryant added the draft proposals would be consulted on, with final recommendations made early next year – though stressed the government would need to table a motion to implement them. A minister told the Guardian it was “contrary to natural justice” to dictate how MPs could use their spare time and said Johnson’s amendment was a “bollocks” plan that could be “completely insignificant” because the interpretation of too much time on another role might end up being so loose that barely anyone would be affected. A former minister revealed they had put other roles “on ice” while waiting for clarity, and was exasperated at cabinet minister Anne-Marie Trevelyan suggesting in three separate interviews on Wednesday that the number of hours worked a week in other jobs should be capped at 10, then 15, then 20. During the debate, Labour accused ministers of putting parliament and democracy “into disrepute” by “ripping up a 30-year consensus on how we enforce standards in this place”. Thangam Debbonaire, the shadow Commons leader, accused Johnson of tabling a “wrecking amendment” and said it would only “water down” genuine attempts to crack down on MPs’ second jobs. “It will be yet more warm words but no action,” she added. However, Jacob Rees-Mogg, her opposite number in government, said it was “an historic strength of our system, that MPs should have a wider focus than the Westminster bubble”. He insisted an MP’s job serving their constituents should take “supremacy”, but believed they should “maintain connections to the world beyond so that we may draw on the insight and expertise that this experience offers”. Some Conservatives raised concerns. Nigel Mills said change had been needed “for a long while” but that the government should be “careful that we get this right”. He warned that people would expect “due consideration” of the issue and that “fair, consistent and enforceable” rules were brought in which “don’t just leave crazy loopholes”. Mark Fletcher, a Tory MP who sits on the standards committee, said people should be “working with [it], rather than instructing it”. He added it was “far from clear” how it should be decided whether an outside job was “within reasonable limits”. And Charles Walker, a Tory MP, hit out at accusations that parliament was a “cesspit and full of crooks and rogues”. He said: “We’ve all suffered from this. I’m not voting for any motion, a plague is deserved on all of our houses.”