Prime Minister Boris Johnson said Tuesday he backs proposals for British lawmakers to be barred from acting as paid political consultants and advisers, after a sleaze crisis hit his government.

In a letter to parliament's speaker, Johnson said he supported proposals put forward in a 2018 report by a watchdog committee on standards that would ban MPs from external consultancy and advisory work.

The British leader added he also backed updating the code of conduct for lawmakers to ensure any outside work was done "within reasonable limits and should not prevent them from fully carrying out their range of duties".

The move follows his ruling Conservatives facing a slew of high-profile sleaze allegations in recent weeks, largely centred on some of its lawmakers with lucrative second jobs.

The crisis erupted after Johnson tried -- and failed -- to overhaul how parliament's watchdogs system operates after Tory MP Owen Paterson faced suspension over lobbying ministers for two firms that had him on the payroll.

It soon emerged numerous other MPs had high-paying second jobs, in particular Geoffrey Cox, a senior lawyer and former attorney general.

He has been accused of using his parliamentary office for outside legal work, which has netted him more than 6 million pounds ($8 million, 7 million euros) since becoming an MP in 2005, on top of his annual MP's salary -- currently around 82,000 pounds.

Cox denies breaking the rules.

'Corrupt and contemptible'

UK MPs are permitted to hold second jobs, as long as they declare them, but are not allowed to use their parliamentary offices or resources for such work.

Paid lobbying is also forbidden, with wrongdoing accusations probed by parliamentary standards watchdogs.

Johnson's spokesman told reporters Tuesday that the British leader had acted now "in light of the recent issues that have come forward".

"It's imperative we put beyond any doubt the reputation of the House of Commons and that's why the PM has written to the Speaker to put forward his view," he said.

However, the spokesman added Johnson did not support banning lawmakers from all second jobs.

"(He) still believes that they can have a role to play in helping inform the decisions of MPs within the requisite boundaries and rules," he said.

"But the Prime Minister agrees that there may be cases where outside interests can lead to undue influence in the political system and that's what we're seeking to address."

The main opposition Labour party is set to introduce a vote on Wednesday to bar MPs from being paid directors as well as parliamentary strategists, advisors or consultants.

"This shouldn't be a controversial statement," its leader Keir Starmer said Tuesday, as he kept up his attacks on Johnson over the issue.

"What the prime minister and the government have done in the last two weeks was corrupt and contemptible," he added.

"It's not a one off. It's a pattern of behaviour."