In his speech to the Tory Party conference, the prime minister will present himself as a reformer who is prepared to take difficult decisions, unlike opponents, who take "the easy decision, not the right one".

Mr Sunak will tell the conference hall that politics "doesn't work the way it should" and that his Labour opponent, Sir Keir Starmer, is "betting on voters' apathy."

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The speech will round off what has been a chaotic four days at the party's annual conference in Manchester - an event that has been overshadowed by the announcement that the northern leg of HS2 will not go ahead as originally envisioned.

Instead, services will run between Birmingham and Manchester but they will not be high speed and they will use the existing West Coast Mainline track.

The development prompted Greater Manchester mayor Andy Burnham to accuse the government of treating people in the north as "second-class citizens".

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He warned the government: "To pull that plug here in Manchester would show complete contempt to the city region and to the north of England as a whole."

The Tory mayor for the West Midlands, Andy Street, also warned it would be "an incredible political gaffe" allowing opponents to accuse Mr Sunak of having decided to "shaft the north".

In his speech, Mr Sunak will rail against "30 years of a political system which incentivises the easy decision, not the right one - 30 years of vested interests standing in the way of change".

He will reflect on his first year in Number 10 and acknowledge a "feeling that Westminster is a broken system".

"It isn't anger, it is an exhaustion with politics," he will say.

"In particular, politicians saying things, and then nothing ever changing.

"And you know what? People are right. Politics doesn't work the way it should."

And he will say: "Politicians spent more time campaigning for change than actually delivering it.

"Our mission is to fundamentally change our country."

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As well as the HS2 announcement, Mr Sunak has also been undermined by his predecessor Liz Truss, who drew big conference crowds as she demanded immediate tax cuts to "make Britain grow again".

Mr Sunak has instead compared himself to the late Baroness Thatcher, who tackled inflation before cutting taxes during her premiership between 1979 and 1990.

While Mr Sunak has repeatedly sought to dodge questions over HS2, he did say on Tuesday that the costs of the project had gone "far beyond" what had been predicted, and the sums involved were "enormous".

The HS2 scheme was given a budget of £55.7bn in 2015 but costs have ballooned, with an estimate of up to £98bn - in 2019 prices - in 2020.