Labour has accused the Government of “dirty tricks” ahead of a crunch Commons vote on curbing MPs’ outside interests.

The party said ministers were trying to “water down” measures to ban MPs taking paid consultancies by removing key elements which would ensure action is taken.

The Commons will on vote on Wednesday on an opposition day motion tabled by Labour calling for a bar on “any paid work to provide services as a parliamentary strategist, adviser or consultant”.

In a surprise move ahead of the debate, Prime Minister Boris Johnson announced he supported such a ban, in an apparent attempt to draw a line under the “sleaze” allegations engulfing his Government.

However Labour was furious when ministers later tabled an amendment which simply described this as a “viable approach” and voiced support for work the Commons Standards Committee was doing to update the MPs’ code of conduct.

It would remove measures in the original motion requiring the Standards Committee to come forward with proposals for implementing the ban and then guarantee time in the Commons for MPs to debate and vote on them.

Shadow Commons leader Thangam Debbonaire said: “Labour has put forward a binding motion to start to clean up our politics after the Tory sleaze scandal. The Conservatives are trying to water that down.

“Boris Johnson has been backed into a corner and one minute accepts our motion in a letter to the Speaker but then comes forward with an amendment that will remove the central part that guarantees that action will be taken.

“This is typical Tory dirty tricks.”