An undercover report accused two British former foreign ministers of offering to use their positions to help a private company in exchange for payment.
The allegations against senior Conservative party lawmaker Malcolm Rifkind and top Labour party MP Jack Straw come just months before a general election and echo "cash for access" scandals that caused political uproar in the past.
Rifkind and Straw are the most prominent figures to have faced such accusations, and Straw suspended himself from the Labour party following the publication of the report on Sunday.
In an undercover investigation by newspaper the Daily Telegraph and TV programme Channel 4 Dispatches, reporters pretended to be from a fake Hong Kong company.
According to the report, Straw offered to use his influence to help the company in exchange for payment of £5,000 ($7,700, 6,800 euros) a day.
Rifkind offered to arrange "useful access" to every British ambassador in the world because of his status, the report said.
Rifkind did not immediately respond to an AFP request for comment, but has denied any wrongdoing according to the Telegraph.
In a statement, Straw said he made it clear he would only work for the company after stepping down as an MP as planned, after the election in May.
"I now face the horrible situation in which what I said is being used to suggest wrongdoing when there was none," Straw said.
"I am clear that there was nothing that I said in the meetings which was improper."
A spokesman at David Cameron's Downing Street office said that Rifkind had referred himself to the Parliamentary Commissioner for Standards, which investigates allegations of rule breaking by MPs.
A Labour Party spokeswoman told AFP: "We have seen the disturbing allegations against Jack Straw."
"He has agreed to refer himself to the Parliamentary Commissioner for Standards and in the meantime he has agreed the best course of action is to suspend himself from the Parliamentary Labour Party."
Straw served in the governments of former prime ministers Tony Blair and Gordon Brown as foreign minister and justice minister.
Rifkind, who was knighted in 1997, is chairman of the Intelligence and Security Committee of Parliament that oversees the work of Britain's spy agencies.
He served as defence minister and foreign minister under former prime minister John Major.
According to the report, Straw told reporters he worked "under the radar" to change European Union rules to help a commodity firm that paid him £60,000 ($92,300, 81,100 euros) a year.
Straw also claimed to have used "charm and menace" to convince a former Ukrainian prime minister to change laws on behalf of the same company, according to the report.
The Telegraph said journalists had contacted 12 lawmakers in the investigation, six of whom did not respond and one who said his contacts were not "for sale".