Business Secretary Alok Sharma lacks the “bandwidth” to head a climate conference alongside his cabinet job, MPs and climate experts have warned.
Mr Sharma was appointed president of next year’s COP26 summit in February, after the sacking of former climate minister Claire O’Neill.
But one senior Tory MP said a bigger profile “grand fromage” was required.
A government spokesperson said Mr Sharma had been engaging with over 40 countries ahead of the event.
Former Conservative PM David Cameron turned down the chance to head the conference, which is due to take place in Glasgow in November next year.
Ex-foreign secretary Lord Hague was also involved in discussions, but will not be taking on the presidency either.
Former Foreign Office minster Tobias Ellwood, who chairs the Commons defence committee, said the UK needs a “grand fromage” to host the event.
Someone, he argues, who can “march into any door of any president or prime minister” and is “free from the machinations of Westminster”.
“It’s got to be the likes of David Cameron, William Hague, somebody of that order that is familiar with the international scene,” he added.
Mr Ellwood said that now the US President-elect Joe Biden had appointed former presidential nominee John Kerry as his climate change envoy, the UK should look for someone with similar “gravitas.”
Richard Black, director of the Energy & Climate Intelligence Unit, told the BBC while Mr Sharma’s experience as a former international development secretary meant he had “an understanding of the developing world”, he had so far “struggled to devote enough time to COP26”.
“I wonder how he will find the bandwidth next year to fully engage with the climate process alongside helping businesses through Covid and Brexit.”
In the run up to the landmark Paris Agreement in 2015, the then French Foreign Minister, Laurent Fabius, held the COP Presidency.
“The story goes that he met every single delegation chief before the summit even happened,” said Mr Black.
Nick Mabey, the chief executive of climate change think tank E3G, and an unpaid advisor to the UK government on COP26, described the summit as a “political litmus test” of the UK’s international ambitions.
He added that while Alok Sharma was said to be “perfectly good at the hard yards of international diplomacy, he’s overloaded with his day job.”
“It’s a bandwidth issue. And we’re missing a natural communicator,” he said.
However, Mr Mabey said that while there was “some talk” of replacing Mr Sharma with a full-time president, “the international optics of another change of COP leadership would be very bad”.
“A better solution,” he added, would be to “beef up the political and diplomatic support for Alok Sharma so he can focus on the most vital and high level issues.”
The Conservative chair of the environmental audit committee, Philip Dunne, while not calling for Mr Sharma to be replaced, said the job of president should be a full time role.
“Running COP26 is a huge diplomatic and logistic effort, and it relies on all of government pulling together. It makes sense for an experienced and dedicated senior minister to lead this work.”
Labour’s Barry Gardiner, a former shadow minister for international climate change, said: “President of COP is a full-time job. So is being business secretary.
“The prime minister was foolish to think one person, however talented, could do both.”
But Sam Hall, the director of the Conservative Environment Network, said that Mr Sharma was doing the necessary legwork in advance of the summit.
“He’s been joining video conferences and getting on planes as part of his COP role, and he’s supported by a good team.
“I think he’ll stay in the job, and it would be disruptive to change the presidency at this stage.”
A government spokesperson said: “Alok Sharma is coordinating efforts to drive action on climate change across the globe ahead of the UK hosting the COP26 climate conference next year.
“This includes engaging directly with over 40 governments as well as attending dozens of major international events virtually to bring the world together to focus on tackling climate change.”