Scotland Yard is looking into a complaint that Deputy Prime Minister John Prescott broke the law by allegedly having sex with his secretary in his Whitehall office.
The formal complaint - in letter form - was sent to the Metropolitan Police Commissioner Sir Ian Blair by Glaswegian Alistair Watson.
It came as Mr Prescott pulled out of a television interview which would have been his first since news of the affair broke.
The Deputy Prime Minister had been due to appear on BBC1's Sunday AM programme but cancelled after aides said he wanted to be with his wife, Pauline.
He pulled out before Friday's Cabinet reshuffle in which he lost his department and was replaced on the programme by Chancellor Gordon Brown.
A spokesman for AM said: "We had an agreement in principle with him when he was still in charge of local government.
"But he has now decided he no longer wishes to talk."
The official complaint about Mr Prescott's extra-marital activities was put forward by Mr Watson, a retired police officer.
He cited the case of a Greater Manchester police officer who was sentenced to 200 hours' community service after he had sex with a woman three times at her home while he was on duty.
According to Mr Prescott's mistress and diary secretary Tracey Temple, she and the deputy prime minister had sex at his Whitehall office while they were supposed to be working.
Extracts of Mr Watson's letter said: "I think, in the interest of equality and justice, there is no reason why Mr Prescott and Miss Temple cannot be prosecuted.
"This is not a malicious thing. If there are rules that apply to ordinary people, somebody like John Prescott should be treated the same, or more harshly."
Mr Watson also said Ms Temple should forfeit any profits made by selling her story to a newspaper.
"I believe this would go some way to deter others in public employ," he wrote.
A spokesman for Scotland Yard said: "Officers will consider the letter and how to respond in due course."
Although Mr Prescott survived the brutal Cabinet reshuffle, he has been stripped of the responsibilities of his department.
He has kept a low profile since lurid details of his private life surfaced more than a week ago.
A spokesman for Mr Prescott said: "The matter is being looked at. There will be a response to parliament in due course." ..SUPL: