Boris Johnson today tried to outflank Sir Keir Starmer as the Prime Minister backed banning MPs from being paid consultants or lobbyists as he tried to quell the sleaze row ahead of a crunch vote.

The PM has written to Commons Speaker Sir Lindsay Hoyle proposing a dramatic overhaul of the rules that could hit the interests of dozens of Tory MPs.  

The pre-emptive move came as Sir Keir prepares to force a vote in the House of Commons tomorrow on barring MPs from holding paid directorships and commercial consultancies. 

Mr Johnson published his proposals this afternoon, just minutes before Sir Keir was due to start a press conference setting out his demands. 

The Labour leader responded to the PM's apparent attempt to spike his guns as he called for an even tougher crackdown, saying that 'enough is enough' and almost all second jobs should be ruled out. 

Mr Johnson said in his letter that the Code of Conduct for MPs should be updated, and endorsed 2018 recommendations from the Committee on Standards in Public Life.

He said the changes should ensure 'MPs who are prioritising outside interests over their constituents are investigated and appropriately punished'. 

Mr Johnson also said he wanted MPs 'banned from acting as paid political consultants or lobbyists'.

The potential tensions over the approach were laid bare earlier today when Cabinet minister Jacob Rees-Mogg suggested it would be impossible to make such rules work. 

Sir Keir was unaware of the PM's intervention at the start of his press conference as he accused Mr Johnson of 'corroding trust in our parliament and the belief that politics is a force for good.'

He added: 'It's time to ban MPs from being paid directors and commercial consultants. That should not be a controversial situation.'

After he was informed of Mr Johnson's announcement, Sir Keir joked: 'So we have won the vote tomorrow already?'  

He added: 'If he is accepting the motion in full, that's a significant victory for us in our work to clear up politics. But I would need to look at how he has put it.' 

Labour deputy leader Angela Rayner later tweeted that the party wants to 'ban second jobs for MPs, with limited exemptions for public service'. 

Sir Keir is pushing the issue in the wake of the Westminster sleaze scandal, triggered by the Owen Paterson lobbying row, which has battered the Conservatives in recent weeks. 

The Labour leader has said it should be a 'point of consensus that paid directorships and commercial consultancies are not jobs for MPs' and 'the only people MPs should be lobbying for is their constituents'. 

Mr Paterson was found by a standards watchdog to have committed an 'egregious' breach of rules by directly advocating for two companies while they were paying him more than £100,000 per year.

The Government blocked his recommended 30-day suspension from Parliament before performing a U-turn after a ferocious backlash, with Mr Paterson then opting to quit as the Tory MP for North Shropshire. 

In his letter today, Mr Johnson said his proposals would ensure MPs 'neglecting their duties to their constituents and prioritising outside interests would be investigated, and appropriately punished by the existing disciplinary authorities'.

'They would also ban MPs from exploiting their positions by acting as paid political consultants or lobbyists,' Mr Johnson added. 

He said: 'The code of conduct for MPs should be updated to state that: ''Any outside activity undertaken by a MP, whether remunerated or unremunerated, should be within reasonable limits and should not prevent them from fully carrying out their range of duties''.' 

That could potentially affect Tory MP Geoffrey Cox, who has been criticised for carrying out a £1million a year legal practice alongside his Commons duties.  

Mr Johnson also backed updating the rules to state: 'MPs should not accept any paid work to provide services as a Parliamentary strategist, adviser or consultant, for example, advising on Parliamentary affairs or on how to influence Parliament and its members. MPs should never accept any payment or offers of employment to act as political or Parliamentary consultants or advisers.'

Labour insists 50 Tory backbenchers and former ministers had been paid by management or consultancy firms over the past year. 

Mr Johnson said the changes could 'command the confidence' of the public, and he wanted them implemented as a 'matter of urgency'.

'The government believes that these two recommendations form the basis of viable approach which could command the confidence of parliamentarians and the public,' he wrote.   

Downing Street said the PM would leave the exact detail of the plans to the House of Commons to decide and finalise. His spokesman said 'it is important in terms of the detailed implementation… that should rightly be for the Commons to take forward on a cross-party basis'. 

Labour is planning to use an Opposition Day debate in the Commons tomorrow to vote on ending paid directorships and commercial consultancies in Parliament. 

Sir Keir responded to the PM's move by claiming the premier had been 'dragged kicking and screaming' to his new position.

He told reporters: 'We've had two weeks of Tory sleaze and corruption. Be under no illusion, the Prime Minister has only done this because his back was against the wall because the Labour Party have put down a binding vote for tomorrow.

'This is a significant victory for the Labour Party, it would not have happened if we hadn't put down that binding vote. This is a prime minister who has shown no leadership on this whatsoever. It is a step forward for standards in public life.' 

Earlier, Mr Rees-Mogg had questioned the viability of Labour's proposals, telling the Conservative Home Moggcast podcast: 'Where do you draw the line? Let me give you a specific example. I am a trustee of the Oxford Union Literary and Debating Trust which is the parent charity of the Oxford Union Society, Oxford's debating organisation.

'It promotes free speech, it supports a very good, active charitable educational objective.

'It takes up a small amount of time each year, it is unpaid. Should MPs be able to be trustees of charities? I think most people would say yes, that is a perfectly reasonable role for them to be involved in.

'But what if they are involved with a charity that is a little bit more work and they actually get paid for it? Should they be involved in that?

'If you say yes, they should be involved in that, can they be doctors? And if you say well yes they can be doctors… are they then allowed to be involved in the pharmaceutical industry?

'Say they have been helpful in developing drugs, have a great deal of knowledge about how drugs are developed and carry on involvement with potentially a start up company that is developing drugs that they may have founded, should they be allowed to continue with that?'

The Cabinet minister said a key question is whether it is 'useful for a member of Parliament to know about different areas and different activities'. 

He continued: 'And if you can't draw the line other than you shouldn't do paid lobbying, how will we decide Labour's motion?

'Is it going to be you can do whatever Keir Starmer does but you can't do any more? Is that what they are proposing?

'So I think drawing lines is extraordinarily difficult and what do voters want? Well they want MPs with experience who contribute.' 

Mr Rees-Mogg said the current rules on paid lobbying are 'really clear and really important' but 'in terms of outside interests it is a much more complex question'. 

Number 10 had said this morning that it would wait to see the exact wording of what Labour was proposing before commenting in detail.      

Asked what the PM's view was on MPs holding consultancies and directorships, his spokesman said: 'I think the Prime Minister has given his view that an MP's primary job is and must be to serve their constituencies and represent their interests in Parliament.

'They should be visible in their constituencies and available to help their constituents with any matters of concern.'