Lord Cameron told Benjamin Netanyahu that the UK will not be proscribing Iran’s Islamic Revolutionary Guard Corps (IRGC) as a terror group, The Telegraph understands.

The Foreign Secretary delivered the message face-to-face to Mr Netanyahu, Israel’s prime minister, and Israel Katz, its foreign minister, according to a senior Whitehall source.

Both Israeli senior politicians are understood to have urged Lord Cameron to take the step when they met in Israel on Wednesday, arguing that Iran’s attack on Israel proved it was necessary.

However, the Foreign Secretary is said to have pushed back firmly, arguing that it would be best if London could still talk to Tehran. “He was pretty blunt,” the source said.

Lord Cameron is understood to have broadly argued the following: “The Iranian foreign minister is no friend of the British Foreign Secretary or vice versa, but we need to be able to pick up the phone. If we proscribed them it would not help the situation.”

The position comes amid renewed pressure from some prominent Tories for the IRGC, a branch of the Iranian military, to be formally prescribed after strikes on Israel last weekend.

Proscription would mean it would become a criminal offence to belong to the IRGC, attend its meetings, carry its logo in public or encourage support of its activities.

The Government has been considering the move for more than a year, with Home Office ministers in the past supportive but the Foreign Office arguing against the change.

Foreign Office figures have warned that taking the step would make it all but impossible for ministers and officials to talk to leading Iranian politicians, cutting off a useful channel of dialogue.

Figures in the US administration, which proscribed the IRGC during Donald Trump’s presidency, are also said to be arguing that it would be beneficial for the UK to maintain contact.

Despite not going for outright proscription, the UK has sanctioned the IRGC multiple times. On Thursday, the IRGC navy was included in a wave of new UK-US sanctions.

It came after Iran fired around 350 drones, missiles and rockets at Israel on Saturday night.

A scrambled Western effort to get Mr Netanyahu not to retaliate is under way amid fears of escalating back-and-forth attacks.

A change in strategy has emerged from the UK Government in recent days as it has become clear a form of retaliation is coming, with the focus turning to trying to minimise the scale of such action.

Grant Shapps, the Defence Secretary, said on Thursday that “in reality” Israel is likely to launch retaliatory action against Iran.

Mr Shapps said during a BBC Radio Four interview that it would be “surprising if Israel in its own self-defence were not inclined to retaliate”.