Israeli police investigators questioned Prime Minister Ehud Olmert on Friday about the corruption scandal that forced his resignation for the first time since Israel ended its offensive in the Gaza Strip.

Olmert, who resigned formally in September, is serving as caretaker prime minister until a new government is formed after an election on Feb. 10.

Police have launched several corruption investigations into Olmert, who has denied any wrongdoing. He quit after his Kadima party elected Foreign Minister Tzipi Livni as his successor.

Livni, a prime ministerial candidate in the vote, failed to form a new government, which left Olmert in charge until then.

Opinion polls show that Kadima trails behind the rightist Likud which is led by Benjamin Netanyahu, now favourite to become the next prime minister.

Olmert saw his popularity ratings recover slightly when he led Israel's military operation in the Gaza Strip together with Livni and Defence Minister Ehud Barak of the Labour party, an outside candidate for prime minister.

Some 1,300 Palestinians, including at least 700 civilians, were killed during Israel's Gaza offensive, according to the Hamas-run Health Ministry in the territory. Israel has lost 11 soldiers and three civilians in the conflict.

Media reports said investigators planned to question Olmert on his appointment of allies to jobs in public corporations when he was trade and industry minister in Ariel Sharon's government.

Late last year, Israel's attorney-general, Menachem Mazuz, said he was considering indicting Olmert for fraud, bribery and tax evasion in a case over fake travel expenses.

Olmert's lawyers said he "totally rejects the suspicions against him" and they were confident he would not be charged.

The Justice Ministry said the charges being considered stemmed from allegations that Olmert submitted duplicate bills to various Jewish organisations abroad and inflated travel costs while serving as Jerusalem mayor and in another cabinet post.

Mazuz's statement, issued two months after police had recommended an indictment, said he offered Olmert the option of a hearing before deciding whether to charge him on four counts of bribery, fraud, false documentation and tax evasion.

Olmert has also been questioned over suspicions he accepted envelopes stuffed with cash from an American fundraiser and using a cabinet post to promote a friend's business interests.