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The ministerial aide at the Department for Science, Innovation and Technology had written to the Prime Minister saying it would save lives.
He has said that Palestinian civilians are facing “collective punishment” as a result of Israel’s siege and air strike campaign following Hamas’s attacks.
Downing Street said that the MP for Peterborough has been asked to leave his job as a parliamentary private secretary.
“Paul Bristow has been asked to leave his post in government following comments that were not consistent with the principles of collective responsibility,” a No 10 spokeswoman said.
Mr Bristow told the BBC he completely understood the Prime Minister’s decision that he regretted having to leave a job he enjoyed.
“But I can now talk openly about an issue so many of my constituents care deeply about,” he added.
“I believe I can do this better from the backbenches rather than as part of the government payroll.”
Mr Bristow’s letter, dated Thursday, appears to have been deleted from his website but remains on Facebook.
He wrote that he is grieved “by the heartbreaking and devastating humanitarian crisis” unfolding in Gaza, having spoken with constituents and meeting members of the Peterborough Joint Mosques Council.
The MP said he welcomed Mr Sunak calling for what he has termed “specific pauses” in the fighting to allow humanitarian aid to enter Gaza, home to more than two million people.
“A permanent ceasefire would save lives and allow for a continued column of humanitarian aid to reach the people who need it the most,” Mr Bristow added.
“The brutal Hamas attacks against innocent civilians are unforgivable.
“Hostages need to be released.
“It is challenging to understand how the present strategy of bombing Gaza will lead to the release of hostages.”
He accompanied an image of the letter on social media saying that Palestinians should not “suffer collective punishment for the crimes of Hamas”.
Labour suspends Andy McDonald after speech at pro-Palestine rally
Labour has suspended its MP Andy McDonald, claiming comments he made at a pro-Palestine rally were “deeply offensive”.
Mr McDonald, who will sit as an independent MP for Middlesbrough while an investigation takes place, used the phrase “between the river and the sea” in a speech during a demonstration at the weekend.
He said his choice of words was part of a wider “heartfelt plea for an end to the killings”.
“The comments made by Andy McDonald at the weekend were deeply offensive, particularly at a time of rising anti-Semitism which has left Jewish people fearful for their safety,” a Labour spokesman said.
“The chief whip has suspended the Labour whip from Andy McDonald, pending an investigation.”
In a video shared by Mr McDonald on X, formerly known as Twitter, of his speech at the rally, he said: “We will not rest until we have justice. Until all people, Israelis and Palestinians between the river and the sea can live in peaceful liberty.”
He went on to chant “free Palestine”, alongside the crowd.
In a statement published on social media, Mr McDonald said he was saddened to be suspended, but would co-operate fully with Labour’s investigation.
“These words should not be construed in any other way than they were intended, namely as a heartfelt plea for an end to the killings in Israel, Gaza and the occupied West Bank, and for all peoples in the region to live in freedom without the threat of violence,” he wrote.
“I will be happy to explain these views to the investigation when it convenes and trust that the whip will be restored.
“In the meantime, for the sake of humanity, I hope and pray that we see an end to the war in Gaza, and steps are taken towards a lasting peace.”