Andrew Bridgen has been suspended as a Conservative MP for spreading misinformation about Covid vaccination.
It comes after the North West Leicestershire MP posted a tweet that compared vaccines to the Holocaust.
Tory chief whip Simon Hart said the comments had "crossed a line" and caused great offence.
Prime Minister Rishi Sunak also condemned the remarks, calling the comparison "utterly unacceptable".
Mr Hart said Mr Bridgen would lose the party whip - meaning he will sit as an independent - while a formal investigation takes place.
"As a nation we should be very proud of what has been achieved through the vaccine programme," the chief whip added.
"The vaccine is the best defence against Covid that we have. Misinformation about the vaccine causes harm and costs lives."
The BBC has contacted Mr Bridgen for a comment.
The MP is currently serving a five-day suspension from Parliament for breaching parliamentary rules on registering financial interests.
Mr Bridgen was previously critical of policies like lockdown and vaccine passports but he praised the development of Covid vaccines, and tweeted proudly when he received his doses.
However, last autumn he began to make increasingly baseless claims including that vaccines were killing many people and that the damage was being covered up.
At first, he began highlighting some real, but rare, instances of genuine vaccine injury and misinterpreting real data to suggest these cases were more common than the research suggests.
In recent weeks, this rhetoric has increased.
Posting a link to an article on vaccines earlier, he said: "As one consultant cardiologist said to me, this is the biggest crime against humanity since the Holocaust."
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