Tricia McDaid, a former political journalist and press officer at Labour party headquarters, said the deputy prime minister “jumped” on her at parties and once turned up uninvited at her home, hoping for sexual favours.

She said yesterday: “He just leapt on me at one party and his tongue was halfway down my throat.”

Such was Prescott’s reputation, she said, that she resorted to wearing trouser suits to avoid his wandering hands in the lifts at his Westminster office. She added that she was too afraid to protest at the time for fear of losing her job.

Prescott yesterday denied the allegations but they will add to the problems encircling the 67-year-old deputy prime minister and threatening his political future.

Friends have said that only pleas from his wife Pauline, 66, stopped him from resigning last week after claims that he had had a two-year affair with a civil servant in his private office. His wife is said to have forgiven him, but the woman involved has now sold the diaries of her love affairs to a tabloid newspaper for £250,000.

In extracts of her diaries published today, Prescott’s diary secretary Tracey Temple claims she performed oral sex on the deputy prime minister in his Whitehall office.

She said he had also taken her back to his grace-and-favour flat at Admiralty House for sex immediately after the pair had attended an Iraq war memorial service at St Paul’s Cathedral with the Queen.

Temple also claims she was driven around by government drivers late at night and said Prescott exploited his power for his own sexual gratification.

McDaid, 45, who has not asked for money, claimed she fell an unwilling victim to Prescott’s advances when she was a political journalist and later a senior Labour press officer.

She said that he turned up at her home at midnight hoping, she believed, for a sexual encounter.

McDaid also said that Prescott boasted he had a dossier of people in the Labour party who had slept with one another.

She said he would jump on unsuspecting women at parties and that she came close to slapping him in the face on several occasions because of his boorish behaviour.

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