UK MP Rifkind quits over 'cash for access'

A British former foreign secretary says he will leave parliament after a "cash for access" scandal exposed in an undercover investigation.

Malcolm Rifkind, who was first elected in 1974 and first served in government under Conservative prime minister Margaret Thatcher, said he would not seek re-election.

"I have concluded that to end the uncertainty it would be preferable ... to step down at the end of this parliament," he said in a statement.

The British parliament is being dissolved on March 30 ahead of a general election on May 7.

Rifkind also said he was resigning the chairmanship of the intelligence and security committee, which oversees Britain's secret services.

But he hit back at the accusations levelled against him in a joint investigation by Channel 4 and the Daily Telegraph, saying they were "contemptible".

Rifkind was suspended on Monday from the ranks of Prime Minister David Cameron's Conservative Party in parliament pending an investigation of the claims.

Rifkind and fellow MP Jack Straw, from the opposition Labour party and also a former foreign minister, are accused of offering to use their positions to help a private company for cash.

In a sting by undercover reporters, the two politicians are said to have offered to act on behalf of a fictitious Hong Kong-based company at a price of at least STG5000 ($A9910) a day.

Rifkind said he could arrange "useful access" to every British ambassador globally and complained to an undercover reporter that he received "no salary" despite his income as a member of parliament.