Ehud Olmert's tenuous grip on power weakened further yesterday when officials of his ruling Kadima party suggested that he would not contest the leadership primaries in September.

Already reeling from a corruption scandal, the fallout from the disastrous war in Lebanon two years ago and poor opinion poll ratings, the Israeli Prime Minister is being asked not to run for re-election by concerned members of his own party.

Today Mr Olmert will be questioned for the third time by police investigating allegations that he accepted bribes, in the form of cash stuffed into envelopes, from Morris Talansky, an American businessman.

Mr Olmert has announced that he will step down from office if an indictment is filed against him. Mr Talansky is currently in Israel for a five-day interrogation into the affair.

“The Prime Minister is trying to hold out for as long as possible, with little thought of how this will affect the country both domestically and diplomatically,” a high-level Kadima party official said, adding that many in the party are pressuring Mr Olmert to announce formally that he will not run in the primaries himself.

The Prime Minister's damaged reputation has triggered a succession battle from party rivals such as Tzipi Livni, the Foreign Minister, who is seen as the front-runner, Shaul Mofaz, the Transport Minister, and Avi Dichter, the Public Security Minister.

Ms Livni has built her reputation on her work as Justice and Foreign Minister, as well as her past experience in Mossad, the intelligence agency. However, it is her pristine record that has captured public interest, especially after Mr Olmert's numerous scandals.

“Everyone abroad loves Livni, but domestically she is untried. Her squeaky-clean reputation may hurt her when it comes to the back-room deals necessary to bring together a coalition,” an associate of Mr Olmert said.

In spite of the mounting pressure for him to go, the Prime Minister has proved adept at clinging to power. Political experts predicted that he could hold on for three to nine months in office, beyond the party primaries. Whoever won the Kadima primaries would have until late October to form a coalition, after which opposition parties would be expected to file motions to disband parliament and force early elections.

Mr Olmert's popularity ratings have remained low throughout his premiership, with his approval dipping below 20 per cent after the the war in Lebanon. A recent poll by the daily Yediot Ahronot indicated that less than a quarter of Israelis believed that Mr Olmert should remain in power, while less than half supported the current diplomatic initiatives he was taking on behalf of the state.

Next week, Mr Olmert will sit at the same table as President Assad of Syria, at the Mediterranean Union summit in Paris. Previous stipulations that the two would meet behind closed doors have not been confirmed by the Syrians or Israelis, although President Sarkozy of France is said to be pressing for direct talks between the two countries.

Peace negotiations between Israel and Syria broke down in 2000 and leaders from the two countries have never met face-to-face.

Israelis have also remained sceptical over the ceasefire that Mr Olmert negotiated with the Hamas-controlled Gaza Strip three weeks ago. Near-daily violations of that truce have led many to suggest that it is a ceasefire in name alone.

The great survivor

March 2006 Ehud Olmert was cleared of wrongdoing in the sale of a Jerusalem apartment, but the government watchdog queried his purchase of one in Tel Aviv. The case was closed this year

December 2006 He ignored calls to resign after he acknowledged for the first time, accidentally, that Israel had nuclear weapons

January 2007 An investigation was launched into allegations that, as Finance Minister, he had tailored a 2005 bank tender to favour a friend. The case was dropped in November

April 2007 He clung on in the face of repeated calls to resign after the Winograd commission's preliminary report accused him of “serious failings” in the 2006 Lebanon war

September 2007 A criminal investigation was opened into his purchase of a home in Jerusalem

October 2007 An investigation opened into allegations of corrupt favours as Industry, Trade and Labour Minister in 2003

May 2008 Ehud Barak, the Defence Minister, called on him to resign in the face of the corruption investigation. Tens of thousands of protesters rallied in Tel Aviv. Olmert said that he would resign if indicted

June 2008 He struck a last-minute deal with his Labour coalition partners less than ten hours before the Knesset was due to begin deliberations on a Bill to dissolve parliament