Channel 4 has called on the broadcasting regulator to investigate its cash-for-access sting on two former foreign secretaries after criticism over its reporting of the allegations.

The Parliamentary Commissioner for Standards cleared Sir Malcolm Rifkind and Jack Straw and said the "damage" done to the former MPs could have been avoided if Dispatches and The Telegraph had "accurately reported" the exchanges they had filmed.

But the newspaper said it believed voters would find it "remarkable" that Parliament investigates the misconduct of its own members while Channel 4 issued a defiant statement defending its journalism and took the unprecedented step of asking Ofcom to look at the case.

A Channel 4 spokesman said: "This programme raised important questions which concern voters about how senior politicians are able to use their public office for personal financial gain. This is a matter of public interest and was a legitimate journalistic investigation.

"We're confident in our journalism and have decided to take the unprecedented step of inviting our statutory regulator Ofcom to investigate it.

"Full transcripts of the interviews are in the public domain and we are in the process of making the programme available on All4, our online platform, to enable people to make up their own minds."

Downing Street said Prime Minister David Cameron welcomed the fact that Sir Malcolm and his family can "now put this distressing episode behind them".

A No 10 spokesman said: "The Prime Minister welcomes today's report by the Parliamentary Commissioner for Standards which has cleared Sir Malcolm Rifkind following allegations made earlier this year. The Commissioner makes clear that Sir Malcolm did not breach the rules on paid lobbying.

"After a long and distinguished career in the House of Commons, the Prime Minister welcomes the fact that Sir Malcolm, and his family, can now put this distressing episode behind them."

mfl