Rishi Sunak has been seeking to speak to Benjamin Netanyahu, the Israeli prime minister, for more than 36 hours to urge restraint over Iran’s recent strike without the call taking place.

Downing Street at first said that the Prime Minister was due to speak to Mr Netanyahu on Monday, and then that changed to Tuesday.

By early afternoon on Tuesday, the call had still not happened.

Israeli media outlets have reported that Mr Netanyahu was refusing to take calls from world leaders seeking to influence the response to Saturday night’s attack.

An Israeli official denied reports that Mr Netanyahu is refusing to take Mr Sunak’s, call but did not specify when it will take place.

Downing Street denied that the UK – which supplied RAF jets to help thwart Iran’s barrage – was being “taken for granted” by Israel and suggested Mr Netanyahu’s other commitments meant a call had not been possible.

The Prime Minister’s official spokesman said: “He has obviously been in discussions with his war cabinet.

“The Foreign Secretary and Defence Secretary have been speaking to their counterparts.”

The spokesman added: “Our position has been made very clearly. We are now working with allies in the region, including Israel, to de-escalate the situation.”

Mr Sunak said told MPs on Monday that he would speak to Mr Netanyahu “shortly” to express solidarity with Israel “and to discuss how we can prevent further escalation”.

The Prime Minister said “all sides must show restraint,” and said the UK was “working urgently with our allies to de-escalate the situation and prevent further bloodshed”.

He added: “We want to see calmer heads prevail and we’re directing all our diplomatic efforts to that end.”

Since Tehran’s air strikes, some Tory MPs have renewed calls to ban Iran’s Islamic Revolutionary Guard Corps (IRGC) as a terrorist organisation.

Senior Tories including Sir Iain Duncan Smith, the former Tory leader, and Suella Braverman, the former home secretary, have urged the Prime Minister to proscribe the group as a terrorist organisation.

But Home Office minister Laura Farris told LBC: “I don’t think there’s any disagreement, actually, on the principle.

“We’re not for a second defending the IRGC. We’re simply saying that maintaining that channel with Tehran at this moment in time is, at present, in our national interest.”

She also told Sky News: “Nobody is denying that they are a malign force. We have repeatedly sanctioned both individual commanders and the IRGC more generally, so that puts very severe restrictions on their ability to move and on other freedoms that they would have had. We are not suggesting they are not a problem.”

Mr Sunak has indicated that any further action could be co-ordinated with the UK’s allies in the G7 group of major democracies.

The United States has already designated the IRGC as a terrorist organisation.