Tel Aviv - Israeli Foreign Minister Tzipi Livni demanded Thursday that caretaker Prime Minister Ehud Olmert vacate his office immediately.

She called on Olmert, who resigned already in late September and therefore cannot step down again by law, to take a vacation until the early elections are held on February 10.

That would allow Livni, who is also vice prime minister, to take his place and serve as acting premier until the elections, which would likely boost her chances.

Livni made the demand a day after Israel's attorney general announced after a lengthy police investigation that Olmert would be indicted on charges of corruption.

Attorney General Menahem Mazuz noted his decision would be final only after a hearing to which Olmert and his lawyers are formally entitled. The hearing is expected to take place after the elections.

Olmert has vowed to continue to head the caretaker cabinet until a new government is formed within up to 42 days after the elections. That means he could stay in power for another four months.

The calls on him to vacate his post sooner intensified immediately after the attorney general's announcement.

"The prime minister must take a vacation. There is no other option," Livni told leading members of her and Olmert's ruling centrist Kadima party at the movement's headquarters near Tel Aviv.

Aides said she planned to gather broad support within Kadima's leadership by pressuring Olmert, who could become the first Israeli premier to be indicted.

"The prime minister like every Israeli citizen is innocent until proven guilty, but citizen Olmert must fight the struggle for his innocence from his home and not from the prime minister's seat," Livni said.

She said Israel could not "bear" a caretaker premier who was about to be indicted yet continued to fill his post and lead the country.

Mazuz made said after studying the body of evidence collected by police, he planned to recommend Olmert be indicted over the so-called "Rishon Tours" affair.

The 63-year-old Israeli leader is suspected of having multiple- billed travel expenses while serving in public office in the years before he was elected premier in March 2006.

Mazuz said Olmert accumulated some 85,000 dollars by submitting bills for the same journey more than once to more than one body, including the state.

These included such institutions as the Yad Vashem Holocaust memorial centre in Jerusalem, the Simon Wiesenthal Centre and the World Jewish Congress.

The indictment was likely to include charges of fraud and breach of trust, Mazuz said in an announcement sent to Olmert and the media.

The Israeli leader reiterated his denial of the charges, and even accused the attorney general and state prosecutors of carrying out a "planned ambush" against him.

Olmert allegedly committed the offences while serving as mayor of Jerusalem and as trade and industry minister between 2002 and 2006. Rishon Tours, the travel agency he used, would send the bills for his flights to the various bodies.

At times the bills submitted were for amounts "significantly higher" than those paid to airlines, Mazuz said. At times, the flight routes were "fictitious" and Olmert did not fly via them at all, he said.

The money was transferred to a special bank account managed by the Rishon Tours travel agency and used for "dozens of private trips" abroad made by Olmert and his family, as well as to upgrade his business flights.

Mazuz stressed that the travel agency acted on the orders and with the knowledge of Olmert and his office manager Shula Zaken, who is also to face an indictment.

Israeli legal experts said Olmert was likely to deny he had any knowledge of fraud and maintain he left it to his office to book his trips.

But the attorney general added that Olmert had been hiding the account managed by Rishon Tours from the state comptroller, and had failed to report on the money he kept in it to the tax authorities.

The Israeli legal advisor accused Olmert of "abuse of his position" and "systematic fraud" over a period of years.

The affair, also dubbed "Olmertours" by the Israeli media, is one of several for which Olmert is being investigated. The suspicions arose during a police investigation into another affair in which the Olmert is suspected of having accepted large sums of cash from Jewish American businessman and fundraiser, Morris Talansky.

That case remains open as Talansky, the key witness, suddenly broke off his cooperation with Israeli police and prosecutors for fear he may be indicted himself in the US. dpa