The head of a UN inquiry into last summer's conflict between Israel and Gaza said on Monday he would resign after Israeli allegations of bias due to consultancy work he did for the Palestine Liberation Organization.

Canadian academic William Schabas was appointed last August by the head of the United Nations Human Rights Council to lead a three-member group looking into alleged war crimes during Israel's military offensive in Gaza.

In a letter to the commission, a copy of which was seen by Reuters, Schabas said he would step down immediately to prevent the issue from overshadowing the preparation of the report and its findings, which are due to be published in March.

Schabas's departure highlights the sensitivity of the UN investigation just weeks after prosecutors at the International Criminal Court in The Hague said they had started a preliminary inquiry into alleged atrocities in the Palestinian territories.

In the letter, Schabas said a legal opinion he wrote for the Palestine Liberation Organization in 2012, for which he was paid $1,300, was not different from advice he had given to many other governments and organizations.

"My views on Israel and Palestine as well as on many other issues were well known and very public," he wrote. "This work in defence of human rights appears to have made me a huge target for malicious attacks ..."

Netanyahu renews calls to scrap inquiry

The resignation prompted Israel's prime minister Benjamin Netanyahu early Tuesday to renew his calls to disband the inquiry.

"This is the same body that only in 2014 passed more resolutions against Israel than against Iran, Syria and North Korea combined," said Netanyahu. "Hamas, other terrorist organizations and the terror regimes around us are the ones who need to be investigated, and not Israel."

Israel had long criticized Schabas's appointment, citing his record as a strong critic of the Jewish state and its current political leadership. Schabas said his work for the PLO had prompted the Human Rights Council's executive on Monday to seek legal advice from UN headquarters about his position.

"I believe that it is difficult for the work to continue while a procedure is underway to consider whether the chair of the commission should be removed," he wrote.

The commission had largely finished gathering evidence and had begun writing the report, he added.

The commission is looking into the behaviour of both the Israelis and of Hamas, the Islamist movement that controls Gaza and calls for the destruction of Israel.