Boris Johnson refused to give Nicola Sturgeon an official role in the Glasgow COP26 climate summit, according to the event's former co-ordinator.
Claire O'Neill said she had made the suggestion in a bid to end the "stand-off" between the UK and Scottish governments over the global conference.
She said Mr Johnson had "heartily and saltily" rejected the proposal.
Ms O'Neill also accused the Scottish government of behaving "disgracefully" ahead of the conference.
The key UN-led summit is due to be held in November at the Scottish Events Campus, which includes the Armadillo and the SSE Hydro.
Ms O'Neill claimed the Scottish government had been contracting buildings from the site which should instead be used by the climate change conference.
The Scottish government later confirmed it had booked the Glasgow Science Centre, which sits opposite the events campus, for the duration of the summit - but said that this had been done after the COP26 organisers had booked what they needed.
A spokesman said it was not surprising or unreasonable for the government to have a base of its own when the event is happening in Scotland, and pointed out that Ms Sturgeon, the Scottish first minister, had been invited to and attended the previous three COP summits.
Ms O'Neill is a former Conservative minister for energy and clean growth who stood down as an MP ahead of the last general election.
She had been co-ordinating plans for the COP26 summit, but was stripped of her role as president last week - and will be replaced by a serving government minister.
Speaking to the BBC's Today programme, she claimed that the prime minister had admitted to her that he "doesn't really get" climate change.
And she said there was "huge lack of leadership and engagement" on the issue from the UK government, adding: "The prime minister has made incredibly warm statements about this over the years.
"He's also admitted to me that he doesn't really understand it. He 'doesn't really get it', I think is what he said."
Ms O'Neill said it was the prime minister himself who chose Glasgow as the location for the summit, but she had been told by people involved that the original analysis for the cost of the event was "hundreds of millions of pounds off track".
She also said she had been told that "the Scottish government has absolutely behaved disgracefully and has been contracting buildings from the COP site, for example, that should absolutely be made available to the conference".
She went on to allege that there was a "complete stand-off between the two governments, and that her suggestion had been that we "need everybody in" and that the "playground politics, the yah-boo of this, has got to stop".
And she said Scotland had a "great track record" on the environment, adding: "I did suggest that we give Nicola Sturgeon a job and she was involved in this, which the PM heartily and saltily rebutted."
Mr Johnson was reported to have told a fringe event at the Scottish Conservative conference in September that he did not want to see Ms Sturgeon "anywhere near" the climate summit as it was the UK government that had brought it to Glasgow rather than the SNP.
To be clear - @scotgov wants #COP26 to be a success & will play our full part in making it so. It’s not about Boris Johnson or me - it is about tackling the climate crisis. My commitment is that political differences will not stop me and my government working to make it a success— Nicola Sturgeon (@NicolaSturgeon) February 4, 2020
Ms O'Neill was speaking ahead of the prime minister pledging that 2020 will be a "defining year of climate action" as he announced that a ban on selling new petrol, diesel or hybrid cars in the UK will be brought forward from 2040 to 2035 at the latest.
Mr Johnson unveiled the policy as part of a launch event for the climate summit alongside Sir David Attenborough, but did not answer questions from the BBC's David Shukman about the row.
In a letter to the prime minister, which has been published by the FT newspaper, Ms O'Neill said she had been told he was considering moving the summit from Glasgow to an English venue - an allegation which Downing Street has dismissed.
The Scottish government said there had been a "significant increase in engagement" in recent weeks from the UK government, which has insisted that Mr Johnson is fully committed to tackling climate change.
And Ms Sturgeon tweeted: "It's not about Boris Johnson or me - it is about tackling the climate crisis. My commitment is that political differences will not stop me and my government working to make it a success."
Ms Sturgeon has also requested that the Scottish government's environment secretary, Roseanna Cunningham, be allowed to attend UK Cabinet and sub-committee meetings on climate Change and COP26, which the prime minister has said he will chair.
What is COP26?
The UN summit, known as the 26th Conference of the Parties, will be held in Glasgow in November and see participating countries assess progress on tackling climate change.
It will be attended by countries that have ratified the United Nations Framework Convention on Climate Change (UNFCCC), a treaty which came into force in 1994.
About 200 world leaders will seek to agree a new, long term deal on rising temperatures.
The COP meeting in Madrid last year saw a compromise deal struck on curbing carbon pledges but left a raft of complex issues unresolved.
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