Two separate congressional investigations will begin this week of Mr Clinton's decision to pardon Mr Rich , who fled to Switzerland almost two decades ago after being indicted on more than 50 counts of fraud, racketeering, illegal trade with Iran and evasion of $48 million (33 million) income tax.

Arlen Specter, the Republican chairman of the Senate Judiciary Committee, said that he planned to ask Mr Clinton to testify on the pardon, which was granted two hours before the former president left office after an intensive lobbying campaign. Although President George W. Bush has said that he cannot undo the pardon, both Republicans and Democrats are furious at suggestions that Mr Clinton may have been influenced by Mr Rich's former wife, Denise, a New York songwriter who has contributed hundreds of thousands of dollars to the Democratic Party.

Mrs Rich and Jack Quinn, the former White House lawyer who pleaded Mr Rich's case direct to Mr Clinton during his last night in office, are due to face questions from the Senate committee this week. Senator Specter said that the request to Mr Clinton was "on the analogy of President Ford", who testified after leaving office on his pardon of former President Nixon over the Watergate affair.

Among those who lobbied for the Rich pardon was Ehud Barak, the Israeli prime minister, and Shabtai Shavit, who was the head of Israel's Mossad intelligence agency for seven years until 1996. Although Israeli officials insisted publicly that the pleas reflected the donations to Israeli hospitals, museums and universities by the charitable Rich Foundation, pressure on Mr Clinton for a full explanation will be increased by the disclosure that Mr Rich had close ties with Mossad.

The Telegraph can reveal that Mr Rich's right-hand man in Israel, Avner Azoulay, is a former Mossad operative with 30 years' service. Mr Azoulay has publicly confirmed that Mr Rich played "a key role" in Mossad operations to help Jews to escape to Israel from Ethiopia in the 1980s and from Yemen in the 1990s. According to Mr Azoulay, Mr Rich used his business dealings to establish contacts with government authorities in Yemen that enabled the Jews to travel to a third country and from there to Israel. He used business contacts in Sudan to help Mossad to organise the operation that rescued Ethiopian Jews.

The Telegraph has established that before taking on his role as head of the Rich Foundation in Tel Aviv, Mr Azoulay headed Mr Rich's security and intelligence operation. Attempts to telephone Mr Azoulay were rebuffed by his secretary, who said he had been "taken ill" and would not be at work "for several days". Controversy over Mr Rich's pardon has caught the normally tranquil Swiss village of Meggen, overlooking Lake Lucerne, by surprise. Here, the 66-year-old fugitive has made his home in Villa Rose, an Italian-style house at the end of a cul-de-sac, protected by solid steel gates and an array of security cameras. He was not, however, at home last week.

Other wealthy residents include the flautist James Galway, Switzerland's leading game show presenter Gabriela Amgarten and Ralph Sonnenberg, a brewer from the Netherlands who lives in an imposing castle. Last week neighbours said that Mr Rich was always accompanied by bodyguards. He is also renowned for holding lavish parties. The mayor of Meggen, Hans Bachmann, said Mr Rich was a generous benefactor, giving more than 40,000 towards the building of a concert house in Lucerne. He had also contributed to the cost of building a new opera house in Zurich and had set up a charitable foundation in the nearby town of Zug, where his office is based.

Mr Bachmann said: "He loves classical music and goes to many concerts. But we don't give him more attention than others and he doesn't want it - he is very involved in business and is often in St Moritz and southern Spain." The billionaire's headquarters in Zug are also protected by heavy security, with visitors required to gain clearance through an intercom before being allowed to pass from a luxurious reception area - surrounded by a thick wall of tinted glass - to the lifts to his offices. Visitors were not being admitted last week and calls to his office were not returned.

Bill and Hillary Clinton have caved into their critics by agreeing to pay for almost half of the $190,000 (129,000) in "house-warming" gifts that they accepted shortly before the former President left office. Among the gifts which the Clintons will pay for are two coffee tables and chairs, costing $7,375 (5,017) from Mr Rich's ex-wife Denise. They will also pay $4,920 (3,346) to the film director Steven Spielberg for china; and $350 (238) to the actor Jack Nicholson for a golf driver.

Mr Clinton also announced that his private foundation would pay a large slice of the almost $700,000 (475,000) rent on the office suite that he plans to lease in New York. Critics complained that the rent was higher than the combined cost of the offices of all four other ex-Presidents, all of which is paid for by the American government.