The UK branch of the Black Lives Matter movement has declared its support for Palestine and faced criticism for saying British politics has been “gagged”.

In a tweet from its official account on Sunday which has been shared thousands of times it pledged solidarity with “our Palestinian comrades”.

But the Campaign Against Antisemitism branded part of the tweet a “lie” and called for the anti-racist movement to be one that unites people and not one that “spreads hatred and achieves lasting division”.

A thread from the @ukblm account began: “As Israel moves forward with the annexation of the West Bank, and mainstream British politics is gagged of the right to critique Zionism, and Israel’s settler colonial pursuits, we loudly and clearly stand beside our Palestinian comrades.

“FREE PALESTINE.”

It comes after Labour’s Rebecca Long-Bailey was sacked from her post as shadow education secretary after refusing to take down a tweet on an article containing an allegedly anti-Semitic conspiracy theory.

In response to the Black Lives Matter UK tweet, a spokesman for the Campaign Against Antisemitism said: “The Black Lives Matter movement should embrace solidarity from Jews. There have been calls for violence against us from prominent BLM supporters with no official condemnation.

“Now from the official UK BLM account we hear the lie that fighting antisemitism ‘gagged’ legitimate debate.

“Zionism is the movement for the self-determination of Jews. The right to the ‘self-determination of peoples’ is universal and enshrined in Article 1 of the UN charter. So-called anti-Zionism exclusively denies Jews that universal right and is therefore antisemitic.

“BLM should aspire to be a movement against racism that unifies people and achieves lasting change, not a movement that spreads hatred and achieves lasting division. You cannot fight prejudice with prejudice.”

Karen Pollock, chief executive of the Holocaust Educational Trust, tweeted: “I can’t stop thinking about this. It’s irresponsible, disappointing and dangerous to post something like this to thousands of followers who sincerely want to fight racism. “Gagged”? Gagged by whom? The insinuation is depressingly clear. You can’t fight racism with racism.”