Chris Skidmore has “no regrets” over leaving Parliament, the former Tory said as he warned the party faces its “toughest by-election fight so far” in his seat.

The former MP for Kingswood, near Bristol, formally quit Parliament on Monday after announcing last week that he was resigning the Conservative whip over the Government’s plans to mandate the issuing of new oil and gas licences.

In an interview with the PA news agency, Mr Skidmore said his decision had followed a period of reflection after 18 months in which he had become increasingly at odds Government policy on the environment.

He said: “Taking a decision like I’ve taken, where you decide to bring an end to your political career after nearly 14 years as an MP, it was a personal decision I didn’t take lightly.

“I’d thought about it for some time and, at the start of the new year, I think, probably no different from anyone else reflecting on their own life and whether their role is the right one for them, I decided now was the time.

“I don’t regret the decision and I still think it’s the right one.”

It’s probably the toughest by-election fight that the Conservatives have faced so far

Mr Skidmore had previously announced that he would leave Parliament at the next general election, when his constituency will be abolished, and his decision to step down this week rather than wait until the poll has left some in Westminster puzzled.

Explaining his choice, he told PA: “My decision to resign the whip and resign as an MP is to demonstrate that we cannot continue, as legislators, thinking that on the one hand we’re going to take action to solve the climate crisis, and on the other press on with the status quo of continuing to extract new fossil fuels.”

The decision is also in line with one of his long-held principles that an MP who voluntarily leaves their party should also resign their seat and either stand in a by-election or leave Parliament altogether.

In 2011, after just a year in Parliament, Mr Skidmore introduced a Private Member’s Bill that would have required MPs to do just that.

He told PA: “The constituents should have a voice, so actually it’s on a separate principle dating back 13 years that I’ve also gone and I’ve been consistent on that in the past.”

It is a decision that, he said, has received mixed reactions from former colleagues. Some have been openly critical of his choice to step down from Parliament, while others have sent “touching” messages.

Over the past 18 months, Mr Skidmore – who was commissioned by Liz Truss to review net zero policies in September 2023 – has become increasingly critical of the direction the Government has taken.

As well as abstaining and then voting against the Government on a number of measures, he strongly criticised the Prime Minister’s speech rowing back on net zero commitments in September last year, describing it as “the greatest mistake of his premiership”.

He told PA that Rishi Sunak’s rhetoric remained “a challenge”, saying: “We haven’t demonstrated that, when it comes to net zero, this is about being on the side of hard-working people.

“That’s the Tory mantra and this is about creating jobs, growth, opportunities.

“I believe in markets, I believe in creating net zero markets, most of the rest of the world are creating these new markets. If we’re not involved in these, we will pay the price by having more expensive goods, fewer jobs, less growth.

“And I think that’s a conservative message and I stick by it; obviously it’s just a shame that this administration has moved away from that core message.”

Mr Skidmore’s departure means a by-election will take place in his constituency, most likely in mid-February.

Labour will be hoping to score another victory in the contest, with the Conservative majority only around 11,000 – well below majorities that have been overturned in recent by-elections.

Mr Skidmore said he expects the environment to play a big role in the election, saying: “It was a Labour seat and I held it in spite of that and worked hard on issues of environmental concern about the countryside, the green belt, in order to win residents’ votes, and I earned those votes.

“I’m really sorry to the constituents who feel that a by-election is unnecessary. I think I’m giving them the power and the voice to be able to have their say over who they want to be their next representative, but it’s probably the toughest by-election fight that the Conservatives have faced so far.”

Now he has left Parliament, Mr Skidmore said he plans to continue campaigning on a cross-party basis to promote net zero, working with businesses, communities and local leaders to ensure the policy remains top of the agenda.

He added: “It’s not like I’m walking away simply to go off to the private sector. This is a decision that I’ve made because I’m committed to leading on this net zero policy space for the future.”