Labour hopes to embarrass David Cameron over the cash-for-access scandal by forcing a House of Commons vote on Ed Miliband's proposal to ban MPs from holding paid directorships or consultancies.
The vote comes a day after former Conservative foreign secretary Sir Malcolm Rifkind stepped down as chairman of a powerful Westminster spying watchdog and announced he was ending his career as an MP after being caught by hidden cameras discussing the possibility of working for a fictitious Chinese company.
Sir Malcolm and ex-Labour foreign secretary Jack Straw - also caught in the sting by Channel 4's Dispatches and the Daily Telegraph - have referred themselves for an investigation by the Parliamentary Standards Commissioner which will not be completed until after the May 7 general election. Both deny wrongdoing.
The Telegraph has now reported that Sir Malcolm boasted to the undercover reporters about his contacts with a series of ex-politicians who had served at "a very senior level", including former US secretary of state Madeleine Albright.
"She and I are good friends," he was quoted as saying. "I still have the contacts with all these people who have served at a very senior level. Some of them still do serve - are still active.
"But in addition to that I am involved with the World Economic Forum, Davos, and they have a number of specialist committees - one of which looks at nuclear security, nuclear weapons security. I was a defence minister so it's an area that I have some interest in, so I have contacts in that area as well."
He added: "If you've done the kind of work I've done over the years, without realising it, you find you know an awful lot of people."
Mr Miliband wrote to Mr Cameron earlier this week urging him to "follow my lead" by banning MPs from being paid by businesses to work as directors or consultants while serving at Westminster. Labour MPs and candidates have already been put on notice that the ban will apply to them after the election.
The Labour leader is also considering a possible cap on the amount MPs earn from work outside their parliamentary duties.
But Mr Cameron said Parliament was "enriched" by MPs with second jobs, saying: "I don't favour a complete ban on all outside jobs or interests. What I see from the Labour proposal is actually not outlawing outside business interests, but putting a new set of rules which would allow someone to work as a trade union official but wouldn't allow someone to run a family shop or a family publishing business."
A Labour spokesman said: "We need to act to improve the reputation of our political system in the eyes of the British people.
"MPs are dedicated to the service of their constituents and the overwhelming majority follow the rules. But the British people need to know that when they vote they are electing someone who will represent them directly, and not be swayed by what they may owe to the interests of others.
"Labour MPs and prospective parliamentary candidates have already been put on notice that from the coming general election the party's standing orders will be changed to prevent them holding such second jobs.
"David Cameron once promised change but now defends a discredited status quo and has refused to follow Ed Miliband's lead. This is his chance to vote for an important measure which would help restore trust in politics."
Commons Speaker John Bercow said MPs should not be in Parliament "to add to their personal fortune" and Sir Malcolm and Mr Straw would "cop it" if they were found to have broken parliamentary rules.
The veteran MPs were recorded by reporters posing as representatives of a Hong Kong-based company wanting to expand in to Europe and seeking to recruit politicians to its advisory board.
Sir Malcolm, who first entered Parliament in 1974 and served for more than a decade in the cabinets of Margaret Thatcher and John Major, boasted that he could arrange "useful access" to every British ambassador in the world, while Mr Straw described how he had worked "under the radar" to raise another company's concerns in Brussels.
Mr Bercow told Sky News's Stand Up Be Counted campaign: "It may well be that errors of judgment have been made. If that is so, then they will cop it, they will face the music, they will suffer a penalty as a result.
"My attitude is people should be in Parliament to represent their constituents and to stand up for principles and policies dear to them. People should not be in Parliament to add to their personal fortune."
MPs on the cross-party Intelligence and Security Committee, which scrutinises the activities of MI5, MI6 and the GCHQ eavesdropping station, agreed to do without a chairman for the remaining five weeks until the election, after Sir Malcolm stood down.
The committee has already completed work on its final report of this Parliament - privacy and security in the wake of the revelations about spy agency snooping by US whistleblower Edward Snowden.