THERESA May has accused Labour of "turning a blind eye" to anti-Semitism as she announced new measures to "call out" perpetrators of hatred against Jewish people.

Speaking at a private lunch of the Conservative Friends of Israel in London, the Prime Minister announced the UK was adopting an international formal definition of anti-Semitism as part of its efforts to eradicate the prejudice.

And she said it was "disgusting" that anti-Semitic views were found in British politics, making clear to her audience that she believed this happened mainly within "the Labour Party and their hard-left allies".

Labour has backed the Government's adoption of the International Holocaust Remembrance Alliance definition of anti-Semitism and a spokesman for Jeremy Corbyn said the party believed that "language or behaviour that displays hatred towards Jews is anti-Semitism and is as repugnant and unacceptable as any other form of racism".

But Mrs May said it was the Conservatives who were taking "the firmest stand" against anti-Semitism.

"Let me be clear: it is unacceptable that there is anti-Semitism in this country. It is even worse that incidents are reportedly on the rise.

"And it is disgusting that these twisted views are being found in British politics. Of course, I am talking mainly about the Labour Party and their hard-left allies," she declared.

Last month, Tom Watson, Labour's deputy leader ,made a declaration of support for Israel by singing the anthem Am Yisrael Chai - The People of Israel Live - at a Westminster lunch.

But Mrs May noted: "No amount of karaoke can make up for turning a blind eye to anti-Semitism. No matter what Labour say - or sing - they cannot ignore what has been happening in their party."

In a comment released before Mrs May's speech, a spokesman for the Labour leader said: "Jeremy has consistently spoken out against all forms of anti-Semitism and condemned all anti-Semitic abuse, and set up the Chakrabarti inquiry into anti-Semitism and other forms of racism.

"Its recommendations have already led to far-reaching changes to the rules and practice of the Labour Party. He has also taken decisive disciplinary action over allegations of anti-Semitism, including a series of suspensions and exclusions from membership."

Meantime, Amber Rudd, the Home Secretary, announced the neo-Nazi movement, National Action, is to become the first extreme right-wing group banned as a terrorist organisation.

An order laid at Westminster on Monday to proscribe the group under the 2000 Terrorism Act is due to come into effect on Friday morning.

It will be the first time a group engaged in extreme right-wing activities will be banned under the laws. The move will mean that being a member of the organisation becomes a criminal offence.