The Times has learnt that Miss Temple, 43, a civil servant who is assistant diary secretary to Mr Prescott, 67, went on the bus the day after Labour secured its historic third term. The revelation will put further pressure on Miss Temple, who fled the country on Tuesday as details of the two-year affair were about to break in yesterday’s Daily Mirror.

The Deputy Prime Minister’s office declined to be drawn on Miss Temple, who was at home in Bordon, Hampshire, on pre-arranged leave when details of the affair began to leak. She will be moved to a different department on her return and also faces a rebuke for breaching the Civil Service code, which states that staff have to uphold the political impartiality of the Civil Service.

A senior Whitehall source said: “The rules are clear. You cannot engage in any form of political activity as a civil servant. It is particularly difficult if you work in the private office of a minister.”

Told that the visit was after polling day, the source said: “At the very least it is a breach of the spirit of the rules. Either way, it is not what we would expect.”

Mr Prescott was told on Monday night by the Daily Mirror that it had seen text messages to and from Miss Temple, a divorcée, that indicated that they had been having an affair. Mr Prescott was also told that Barrie Williams, 46, Miss Temple’s partner for the past eight years, had given an in-depth interview to the newspaper. Mr Williams, a driver, was paid £20,000 for his story after he approached the newspaper.

Mr Prescott’s office initially denied the allegation but the minister pointedly did not in his first conversation with the newspaper on Monday night. At 5pm on Tuesday he confirmed that he had been involved with Miss Temple, who has been a civil servant for 20 years and used to work for the late Mo Mowlam.

He was then driven back to Hull in his government car to break the news to his wife Pauline, 64, to whom he has been married for 44 years. The statement, in which he described her as devastated, was issued after he told her about the affair.

Mr Prescott and Miss Temple flirted openly in their Whitehall office but few people knew that they were engaged in a clandestine relationship.

Yet, at the height of their affair, Mr Prescott took Miss Temple to a memorial service for British troops killed in Iraq at St Paul’s Cathedral in 2003 attended by the Queen. Miss Temple also walked side by side with Mrs Prescott to the State Opening of Parliament in 2002, shortly before the affair began.

At Westminster there was surprise but little criticism of Mr Prescott, who was in Hull yesterday at the family home. One minister said: “John will be feeling he has let the side down, let the Labour Party down.” A Downing Street spokesman said: “This is a private matter, as is any discussion between the Deputy Prime Minister and the Prime Minister.”

The Labour Party said that it expected Mr Prescott, a key figure in the local elections, to be back on the campaign trail within days. Mr Prescott was due back in London today for the weekly Cabinet meeting.

Phil Woolas, the Local Government Minister, said: “He is one of the most incredibly able politicians I have worked with. I am very proud to work with him.”

Reaction on the streets of Hull was mixed but one elderly man, passing on his bicycle, shouted out: “He should resign. He should be thoroughly ashamed of himself.”

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