Although the US publicly called for its allies to proscribe the IRGC after the October 7 attacks, The Telegraph understands American diplomats have privately asked the UK not to do so.

The US has not had diplomatic relations with Iran since 1980 and relies on other Western allies including the UK to act as a backchannel with Iran.

Some US officials have privately raised concerns that if the UK was to proscribe the group, Tehran would sever diplomatic ties with London and cut off a key diplomatic backchannel.

On Sunday, Victoria Atkins, the Health Secretary, said IRGC proscription was kept under “constant review” but added: “There is a point of the value of being able to have a direct conversation with the Iranian authorities in the way that has already happened, there is a value in that, to be able to land those messages directly with Iran.”

She also said the police, the security services and courts had the powers that they needed to target those people causing the most concern, noting that the UK had sanctioned some 400 organisations or individuals.

However, Mr Haiat tweeted: “Iran must pay a price for its aggression. The initial price must be the immediate recognition of the Iranian Revolutionary Guards Corps – which launched the extensive terrorist attack last night – as a terrorist organisation.”

Mrs Braverman tweeted that the attack must mark the end of “Western backsliding” on Israel. Last week she said the Government needed to “grow a backbone” and take tough action against the IRGC as the “chief sponsor of global terrorism.”