Rishi Sunak has denied his party is preparing for election defeat and insists his team is “fired up” about winning a full term.

Asked what his message would be to Tory MPs despondent about the party’s lag in the polls, Mr Sunak said he was “entirely confident we can win the next election”.

“I am working to get a first full term. I will show the British people what I am capable of in the time I have now before the election,” he said.

Some Tories fear that Mr Sunak’s five priorities – including halving inflation, cutting debt, and stopping small boats – are out of reach and uninspiring for voters.

But Mr Sunak told reporters on the plane to the G20 in Delhi: “I think we have achieved a lot over the last eight months, and you can start to see the fruit of that work.

“You saw over the summer inflation is coming down, that’s the best thing we can do to help people with the cost of living, energy bills are coming down considerably from where they peaked, that’s going to help people; the number of small boat crossings, of course higher than any of us would like… but for the first time ever they are down on the year before… the plan is working.”

Sky’s poll tracker shows Sir Keir Starmer’s Labour Party with an average lead of 18 points in the polls, with three by-elections looming next month, two of them in safe Conservative seats.

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The prime minister says his party’s narrow victory in the Uxbridge by-election earlier this year, despite losing two other seats on the same night, made him “entirely confident of victory”.

“That’s what a general election looks like, it’s an actual choice between two alternatives on a set of issues of substance. That’s why I feel confident, as we won in Uxbridge we will be able to make great progress,” he said.

Pollster and former Conservative adviser Luke Tryl said in response: “There’s no doubt the Tories outperformed expectations in Uxbridge and you can see why the PM would want to highlight that bright spot after a difficult few months.

“The problem is the factors that helped the Tories hang on in Uxbridge are almost totally unique.

“The harsh electoral reality for the Tories is the other by-election held on the same day where the Tories saw a 24-point swing against them is a far better reflection of where the public mood is today.”

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Last week, reports surfaced that the prime minister’s chief of staff Liam Booth-Smith had told political advisers they should quit their jobs if they didn’t believe the Conservatives could win.

A shake-up of Downing Street staff has been taking place, with the departure of Mr Sunak’s head of communications, and a new strategy director brought in.

The prime minister said: “As you can see we’ve brought some new people in, very high-quality people that are joining the team because they believe that we will win – they are hungry to win, I am hungry to win, and we are fired up to deliver it.”

Mr Sunak refused to commit to offering tax cuts before the next election, saying the “best tax cut I can deliver for the British people is to reduce inflation”.

The Conservatives have had a difficult summer, with their plans to send asylum seekers to live on a floating barge scuppered by the discovery of legionella and crumbling concrete closing schools.

Mr Sunak conceded the timing of the RAAC concrete crisis had been “frustrating” but said ministers were right to act as quickly when it came to light.