JERUSALEM (Reuters) - Israel demanded Britain change its law on Tuesday after reports that ex-foreign minister Tzipi Livni would have risked arrest on war crimes charges over last year’s Gaza offensive, had she not canceled a visit to London.

The legal jeopardy faced by Israeli politicians and military officers could damage Britain’s efforts to play a role in Middle East peacemaking, Israel’s Foreign Ministry said after British media reported a magistrate had issued an arrest warrant for Livni at the behest of lawyers acting for Palestinians in Gaza.

Israeli Prime Minister Benjamin Netanyahu said in a statement he rejected “this absurdity,” which was ultimately aimed at impairing Israel’s ability to defend itself.

Netanyahu’s national security adviser and the Foreign Ministry summoned the British ambassador to convey their dismay.

British Foreign Secretary David Miliband said the government was determined to protect its close ties with Israel.

“Israeli leaders, like leaders from other countries, must be able to visit and have a proper dialogue with the British government,” he said in a statement.

“The procedure by which arrest warrants can be sought and issued without any prior knowledge or advice by a prosecutor is an unusual feature of the system in England and Wales,” he added.

“The government is looking urgently at ways in which the U.K. system might be changed in order to avoid this sort of situation arising again.”

The warrant is the latest in a series of incidents to make life uncomfortable for senior Israelis in Britain in recent years. It was withdrawn, British media said, after Livni, now leader of the opposition, canceled plans to attend a meeting last weekend.

“NATURAL OBSTACLE”

The Israeli Foreign Ministry said: “A lack of immediate and decisive action to amend the anomalies harms relations between the two countries.

“If Israeli leaders cannot visit Britain in an appropriate and respectable manner it will be a natural obstacle to Britain’s wish to fulfill an active role in the Middle East peace process.”

Livni herself, whose low domestic profile has been given a boost by the controversy, brushed off the arrest warrant in a speech in Tel Aviv in which she defended her actions in Gaza.

“Israel had to do the right thing -- condemnation or no condemnation, statements or no statements, arrest warrants or no arrest warrants. This is the role of a leadership,” she said.

Last month, British ambassador Tom Phillips told a group of Israelis concerned at what they called a sharp rise in hostility to the Jewish state in Britain that the government did not support court action against Israeli leaders, but was bound by existing laws.

He indicated it was considering curbing courts’ powers to issue such warrants for the arrest of foreign officials. However, he said Israel’s Gaza offensive a year ago, which caused public dismay in Britain at the hundreds of deaths of Palestinian civilians, had made it more difficult for the government to legislate for that.

International human rights bodies, including a commission set up by the United Nations, have said Israeli political and military officials should answer allegations of war crimes over the three-week offensive launched on December 27.

More than 1,400 Palestinians were killed, while the toll on the Israel side was 13. Israel said it acted according to high military and moral standards during the war.

(Additional reporting by Alastair Macdonald in Jerusalem, Dan Williams in Tel Aviv and Kylie MacLellan in London; Editing by Alastair Macdonald and Andrew Dobbie)