The demonstration took place in Parliament Square as MPs debated calls for an immediate ceasefire in Gaza, which led to chaotic scenes in the Commons.

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The prime minister's official spokesperson said it was "wrong" for the controversial phrase to be used, though stopped short of saying police should have acted over it, adding: "It is rightly a decision for the independent police to make operational decisions on the ground."

Other words were also projected onto the Elizabeth Tower, including "stop bombing Gaza," "ceasefire now", and "stop war now".

But the use of "from the river to the sea, Palestine will be free" has drawn anger from some pro-Israel supporters, who argue the phrase calls for the eradication of the Israeli state.

Some pro-Palestinian supporters reject this, saying it is simply expressing the need for equality for all inhabitants of historic Palestine.

The Campaign Against Antisemitism called it "genocidal language", and said the incident on Wednesday was "a wake-up call for Britain"

A spokesperson told Sky News that weekly marches by pro-Palestinian groups were "making our capital city a no-go zone for Jews and repel law-abiding Londoners", adding: "If our laws are now being made through the medium of threat and violence, our democracy itself is under attack, and those responsible for safeguarding it are in dereliction of their duty."

Tory MP Andrew Percy also highlighted the projection in the Commons on Thursday, saying the slogan was a "genocidal call".

He also criticised police for their lack of action, adding: "For months I've been standing up here talking about the people on our streets demanding 'death to Jews', demanding Jihad, demanding intifadas as the police stand by and allow that to happen."

The Palestinian Solidarity Campaign (PSC), which organised the protest, told Sky News they were not responsible for the projections.

However, the group's director, Ben Jamal, said they were "pleased to see it", adding: "The chant, 'from the river to the sea, Palestine will be free', is used widely by Palestinians and those advocating for Palestinian rights to express the manner by which Palestinian rights are deprived and what is required for them to achieve freedom.

"It speaks to the reality that all Palestinians live under a system of apartheid which deprives them of rights whether as unequal citizens of the state of Israel or under illegal military occupation, in Gaza and the West Bank.

"Palestinians will be free when that system of apartheid is ended, just as South Africans became free when South African apartheid was dismantled."

A spokesperson for the Metropolitan Police said: "This is a chant that has been frequently heard at pro-Palestinian demonstrations for many years and we are very aware of the strength of feeling in relation to it.

"While there are scenarios where chanting or using these words could be unlawful depending on the specific location or context, its use in a wider public protest setting, such as last night, is not a criminal offence."

Leader of the House Penny Mordaunt said authorities were investigating the incident.