Rishi Sunak’s climate credentials were under scrutiny on Friday after the new Prime Minister decided to snub Cop27, amid speculation that he could move to expand the windfall tax on energy companies.

Climate activists and opposition MPs have been urging the new prime minister to go further on his windfall tax as oil and gas giants see profits soar.

The Telegraph reported that Mr Sunak, who alongside Chancellor Jeremy Hunt is seeking out ways to plug a multi-billion pound fiscal black hole, is considering an expansion of the windfall tax that would see the levy potentially increased or expanded to included renewable energy generators.

Downing Street said “nothing is off the table” ahead of Mr Hunt’s autumn budget on November 17.

It comes after Shell avoided paying the levy despite a doubling of profits fuelled by soaring energy prices.

Next month’s financial statement was given as one of the reasons that Mr Sunak will be unable to attend Cop27, the global climate summit due to take place next month in Egypt.

Liz Truss had been due to attend but Mr Sunak, who is expected to visit south London on Friday morning, has decided not to attend.

The move prompted an backlash from campaigners and the opposition, with Labour leader Sir Keir Starmer tweeting: “Britain showing up to work with world leaders is an opportunity to grasp. Not an event to shun.”

Green MP Caroline Lucas said “shame on” Mr Sunak, while Greenpeace UK said the move suggests Mr Sunak does not take climate change “seriously enough”.

A Downing Street spokeswoman said Mr Sunak was focusing on domestic issues including preparations for the autumn budget, which has been delayed from Monday to November 17.

She said the UK will be “fully represented” by Cop26 President Alok Sharma and “other senior ministers”.

“We remain committed to net zero and to leading international and domestic action to tackle climate change. The UK is forging ahead of many other countries on net zero,” she said.

It comes as new polling indicates that the elevation of Mr Sunak to Conservative leader might have registered with approval among some voters.

New polling by YouGov put the Tories on 23% to Labour at 51%, a four percentage point bounce the Conservatives from a week ago.