Israeli Prime Minister Benjamin Netanyahu's wife Sara has been charged with fraud and breach of trust following a long police investigation into allegations she falsified household expenses, the justice ministry said.

"The Jerusalem district prosecutor a short time ago filed charges against the prime minister's wife," the ministry said.

The allegations announced last year are that she and an aide falsely declared there were no cooks available at the prime minister's official residence and ordered from outside caterers at public expense.

The cost amounted to "over 350,000 shekels (over €83,000)", the justice ministry said.

She has denied any wrongdoing.

Her husband is himself under investigation on suspicion of corruption offences.

Sara and Benjamin Netanyahu

In one case, he and family members are suspected of receiving one million shekels (€240,000) worth of luxury cigars, champagne and jewellery from wealthy personalities in exchange for financial or personal favours.

In the other case, investigators suspect the premier of trying to reach an agreement with the owner of Yediot Aharonot, a top Israeli newspaper, for more favourable coverage.

Mr Netanyahu has protested his innocence and vowed to remain in power, saying he is the victim of a "witch-hunt".

He also faces suspicions of government favours that allegedly saw regulatory breaks go to Israel's largest telecom firm Bezeq, in return for favourable coverage of him and his wife by a news website.

Despite his troubles, opinion polls suggest Mr Netanyahu's right-wing Likud party would remain the largest in parliament if elections scheduled for November 2019 were held now.