The former president of the UN climate summit in Glasgow, who was sacked by the Government last week, has claimed Boris Johnson is considering moving the event to an English location.

Former clean growth minister Claire Perry O'Neill made the claims during a blistering attack on the Prime Minister's record on tackling climate change.

She also said that Mr Johnson declined in "salty terms" after being asked to consider "putting aside the devolution battle" with First Minister Nicola Sturgeon for the sake of the climate crisis. 

It comes as the PM prepared to outline new measures, including a ban on sales of new petrol and diesel vehicles being brought forward to 2035.

In a letter to Mr Johnson published by the Financial Times, Ms O'Neill told him: "You promised to 'lead from the front' and asked me what was needed: 'Money, people, just tell us!' Sadly these promises are not close to being met."

She added: "This isn't a pretty place to be and we owe the world a lot better."

She said the PM had not convened the Cabinet subcommittee on climate change that he had promised, adding that the Government was "miles off track" in setting a positive agenda for the COP26 summit in Glasgow in November, and that promises of action "are not close to being met".

Glasgow Times:

READ MORE: Glasgow COP26 climate summit ‘mired in confusion and chaos’

Ms O'Neill also suggested Mr Johnson's personal animosity towards First Minister Nicola Sturgeon is endangering the success of the summit and claimed the Prime Minister is considering relocating the event to an "English location" because of "ballooning costs".

She said: "I am told by COP unit sources that budgets (which I do not see) are ballooning, the team and the Scottish Government are in an extraordinary state of stand-off and that you are considering re-locating the event to an English location.

"I had asked if you would consider resetting your relationship with the First Minister - putting aside the devolution battle for the sake of this vastly more important agenda. 

"I understand you declined in salty terms". 

Referencing the letter, Nicola Sturgeon has said the priority for the upcoming COP26 summit in Glasgow is tackling the climate crisis rather than her relationship with Boris Johnson.

The First Minister wrote on Twitter: "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."

Ms O'Neill's comments came as Mr Johnson was about to outline plans for the summit with a speech setting out Britain's stall as a leader on tackling climate change.

In his speech on Tuesday, he will urge other countries to follow the UK's lead in setting targets to cut their emissions to net zero - with major cuts to greenhouse gases and any remaining pollution offset by measures such as planting trees.

As part of the UK's moves to meet its legal goal to reach net zero by 2050, the Government will consult on bringing forward a planned ban on the sale of new petrol and diesel vehicles from 2040 to 2035 - and earlier if feasible.

The ban, which Government adviser the Committee on Climate Change has called for by as early as 2030, will also include hybrid vehicles for the first time.

At an event attended by Sir David Attenborough, Mr Johnson will call for international efforts to reach net zero as early as possible through investment in cleaner technology and protection of natural habitat - which will also help reverse losses in wildlife.

Mr Johnson said: "Hosting COP26 is an important opportunity for the UK and nations across the globe to step up in the fight against climate change.

"As we set out our plans to hit our ambitious 2050 net-zero target across this year, so we shall urge others to join us in pledging net-zero emissions.

"There can be no greater responsibility than protecting our planet, and no mission that a Global Britain is prouder to serve.

"2020 must be the year we turn the tide on global warming - it will be the year when we choose a cleaner, greener future for all."

Glasgow Times: Claire O'Neill (Getty)Claire O'Neill (Getty)

READ MORE: Scottish Government confirms they are considering inviting Greta Thunberg to Glasgow's COP26

The event will also kick off a year of climate action across the UK, the Government said.

The UN climate talks in November are the most important since the Paris Agreement to curb global warming was secured in 2015.

Countries are expected to deliver more ambitious domestic plans for cutting greenhouse gases by 2030 - as current proposals are not enough to prevent dangerous temperature rises.

Pressure is also on countries to set out long-term plans for cutting emissions, with the science now clear that the world must reduce greenhouse gases to zero in a matter of decades to avoid the worst impacts of climate change.

The run-up to the talks will require a major diplomatic effort from the UK to secure ambitious climate action from countries - at a time when Britain is also negotiating trade agreements with the EU and other nations.

Ms O'Neill, who stood down as a Tory MP at the general election, was sacked as president of the talks by the PM's special adviser, Dominic Cummings, on Friday, with the Government saying the post would be a ministerial role in future.

But Nick Mabey, chief executive of climate change think-tank E3G, said the UK's presidency had got off to a bumpy start with the decision to dismiss her.

Her replacement has a "daunting task" and will need to be a political heavy hitter, with an immense diplomatic effort needed from the UK to steer the negotiations, he said.

While the UK has a legal target to cut emissions to net zero by 2050, the Committee on Climate Change has warned that domestic action to slash carbon dioxide and other greenhouse gases is lagging far behind what is needed - even before the net-zero target was set.

AA president Edmund King said the new target on car sales is incredibly challenging.

He added: "We must question whether we will have a sufficient supply of a full cross-section of zero- emissions vehicles in less than 15 years."

He also raised concerns that hybrids would be excluded from sale under the plans.

Ms O'Neill is also reportedly consulting lawyers about what she claims were "false, distorted and defamatory" briefings about her record, saying Number 10 was "rumoured" to be behind the briefings.

She told the Financial Times she had been considered for a peerage by Downing Street to give her more authority in her UN summit role, but this had now been "firmly rescinded".

Number 10 declined to comment.

A Scottish Government spokesman said: "Discussions are of course taking place in relation to costs, as with any major event, and Scottish ministers expect that all costs associated with COP26 will be borne by the UK Government.

"This includes funding for police as well as the fire and ambulance services to both prepare for and deliver a safe, secure and successful event.

"COP26 is hugely important for tackling the climate crisis and that must be the focus.

"A new president should be appointed immediately to make real progress in building the relationships that will be needed within the UK, and around the world, to deliver a successful outcome from the conference."