Lib Dem leader Sir Ed Davey has insisted he is not just aiming to be a junior partner in a coalition government, saying: "I am a candidate to be prime minister."

He also backed the controversial Jackdaw gas field, which the government is expected to green light later this month, saying it had "passed the climate test" and was compatible with a transition to renewables.

Sir Ed has faced criticism from some in his party that he lacks ambition and the vision needed to cut through in a crowded political field.

He acknowledged the "frustration" felt by some of his MPs that the party was not making a bigger impact - and vowed to set out bold policies in his conference speech on Tuesday.

Sir Ed led the Lib Dems to a record 72 MPs at the 2024 election, making big gains at the expense of the Conservatives in southern England, but the party has since slipped to fourth or fifth in national opinion polls, behind Labour, the Tories, the Greens and Reform UK.

Despite this, the Lib Dem leader claimed his party had an "historic opportunity to do far better than anyone imagines at the moment" at the next general election.

"Because the right wing is split," he said, "and fragmented like it's never happened before in over 200 years of British parliamentary elections.

"If we take that opportunity, and I believe we're showing how we can, we'll be a massive force in the next parliament."

Asked if he wanted to be the kingmaker in the next government, providing support for a party falling short of the 326 MPs needed for a majority, Sir Ed said: "I've got no ceiling on our ambitions.

"I'm a candidate to be prime minister, but what we need to do is make sure that we build on that [election success], area by area, constituency by constituency."

He made clear he will not go into a coalition government with Reform UK and has dismissed suggestions he could do a deal with the Conservatives.

"We've got a moral responsibility to stop Nigel Farage - and indeed stop Kemi Badenoch giving the keys to No 10 to Nigel Farage - I think there could be that sort of coalition on the right and we've got to stop that," he told the BBC.

Asked if he would form a coalition with Labour, he said he did not deal in "hypotheticals".

He said he wanted the Lib Dems to win support across the UK, but the BBC has been told his party's strategy is focused on the 27 seats where they came second in 2024. Of those 27, 20 are held by the Conservatives.

Sir Ed was speaking just before he headed out to visit the wind farm off the coast of Brighton, which he said he had signed off on when he was energy secretary in the Conservative-Lib Dem coalition government a decade ago.

He set out why supporting Jackdaw was not in conflict with his party's stance on tackling climate change, saying: "We're going to need gas for a long, long time as part of our transition, and when I was secretary of state for climate change, I always thought that we were going to need gas, and [Jackdaw] has passed the climate change test."

Sir Ed explained the alternative was shipping in liquified natural gas (LNG) from across the globe, which would be more problematic than using gas from the North Sea, about 150 miles northeast of Aberdeen.

"There's a lot of energy produced in both putting the gas into liquid and then taking it out into gas," he said.

"The carbon footprint of that is far bigger, a lot more damaging for our climate, so this way, not only is it better for the climate, but also tax revenues come to the Exchequer."

However, he told the BBC "the jury is very much out" on the Rosebank oil field, not least because that may not pass the same test on reducing carbon emissions.

And he insisted the Lib Dems were still committed to a transition away from oil and gas, for the climate and also to lower people's energy bills.

"Thanks to President Trump's mad war in Iran, people are paying far higher," he said. "We are paying far higher for that fossil fuel energy, and you've seen over the years how fossil fuels, oil and gas, can be extremely expensive.

"So, the way to get energy bills down, get the economy growing, is to be less dependent on fossil fuels and we want to be."

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