MPs will be forced to drop lucrative outside jobs if they "conflict" with their jobs serving their constituents, according to a proposed new code of conduct.

The MPs' second jobs will be scrutinised by the Parliamentary standards watchdog for the first time in a major crackdown on politicians’ lucrative work away from the House of Commons.

A new code of conduct will require MPs to ensure that any outside work “does not conflict” with their day jobs representing constituents in Parliament.

The change in the rules – which are still to be approved by MPs– will radically cut back the amount of time MPs will be allowed to spend away from their constituents.

It could also make it easier for the Standards Commissioner Kathryn Hudson to stop MPs using their positions to win paid consultancy work outside the House of Commons.

An undercover investigation last year by the Telegraph found Jack Straw and Sir Malcolm Rifkind had offered to use their positions as MPs to win contracts. However they were cleared of wrongdoing by Mrs Hudson.

The new code of conduct for MPs proposes an additional rule, which have been introduced following “recent changes to other rules or issues that have become apparent during investigations”.

It says: “A member who undertakes outside employment must ensure that it does not conflict with his or her responsibilities under the Code of Conduct.”