The ruling body of Britain's main opposition Labour party agreed Tuesday to adopt in full an international definition of anti-Semitism for its code of conduct, after a bitter row that reignited internal criticism of leftist leader Jeremy Corbyn.

Labour's National Executive Committee (NEC) agreed that in dealing with anti-Jewish abuse, it would use the definition and examples drawn up by the International Holocaust Remembrance Alliance (IHRA).

Critics had argued that certain IHRA examples could curb legitimate criticism of the state of Israel.

The debate fed into a months-long row over anti-Semitism in the party, in which MPs and Jewish groups have repeatedly accused Corbyn of failing to clamp down on the problem.

The Labour leader, a veteran pro-Palestinian campaigner, has also been forced to defend his own behaviour in recent months, including from criticism from Israeli Prime Minister Benjamin Netanyahu.

The NEC meeting at Labour's London headquarters lasted several hours, while outside, noisy demonstrators gathered from both sides of the debate.

"The NEC has today adopted all of the IHRA examples of anti-Semitism, in addition to the IHRA definition which Labour adopted in 2016," a Labour spokesman said.

They were adopted "alongside a statement which ensures this will not in any way undermine freedom of expression on Israel or the rights of Palestinians".

Jane Barlow / AP

British Jews felt 'under threat'

However, this statement drew immediate criticism.

Long-serving Labour MP Margaret Hodge, one of Corbyn's most strident critics on the issue, tweeted that the decision was "two steps forward and one step back".

"Why dilute the welcome adoption IN FULL of the #IHRA definition of #Antisemitism with an unnecessary qualification?" she wrote.

The group Labour Against Anti-Semitism added that the clarifying statement "risks giving racists in the party a get out of jail card".

Outside, demonstrator Stan Keable, secretary of the Labour Against the Witch Hunt group, said the fight was wider than the issue of anti-Semitism.

He argued that the IHRA definition was specifically designed to associate anti-Semitism with criticism of Zionism and Israel.

"This whole campaign about new anti-Semitism is a lie," he told AFP.

"This is a struggle between the right and the left wing in the Labour Party. This is a struggle for the control of the Labour Party."

But counter-protester Damon Lenszner said British Jews felt "under threat".

"The far left in any country has always had an anti-Semitism problem, the same as the far right."

In March, British Jewish leaders wrote a joint letter claiming "enough is enough" over anti-Semitism within Labour, and protests were held outside parliament.

The letter claimed a "repeated institutional failure" within the party to tackle the problem and accused Corbyn of siding with anti-Semites "again and again".

Supporters of Corbyn insist he has worked his whole life for peace and against racism.