Andy Burnham is to face his first Prime Minister’s Questions, and an early test of his authority over Labour backbenchers, after setting out his plans for Government.

The Prime Minister made his debut at the Commons despatch box on Tuesday, when he set out plans to devolve more power away from Westminster and into the regions, and to take back public control over utilities and services.

Mr Burnham blamed the legacy of Margaret Thatcher, the austerity era, and Brexit for decades of slow growth, and insisted his plans to change the “failed economic model” would kickstart Britain’s economy.

“Britain is not where any of us would wish it to be,” he told MPs, adding: “Things are not working as they should, life is too expensive and too hard for too many.”

During his Commons outing, he described Britain’s water industry as “a leaking monument to that approach, a country run in the private rather than public interest”.

Throughout his three hour and 23 minute Commons grilling, the Prime Minister declined to say whether there will be tax rises at the October 28 Budget.

But he suggested that his Chancellor John Healey will find money to hike defence spending to 3% of GDP by 2030 by the time of the next spending review.

On Tuesday, the Prime Minister told Cabinet that his Government will have three priorities: cutting the costs of essentials such as childcare and mortgages, regenerating communities, and greater public control over utilities such as water, energy and housing.

But Mr Burnham’s ambitions for overhauling how the UK state operates are likely to be curtailed by the economic headwinds caused by the Iran war.

Government long-term borrowing costs have been sent soaring to their highest levels for 28 years, amid a global bond sell-off partly linked to signs of escalation in the Middle East conflict and the concern that inflation could follow.

The Prime Minister is understood to have invited Labour MPs to Downing Street to woo them over drinks following his turn at the despatch box.

But Labour backbenchers pushing for faster reforms to electoral law could provide Mr Burnham with his first Commons headache on Wednesday, after he has faced Conservative Party leader Kemi Badenoch in his first Prime Minister’s Questions.

Alex Sobel, the Labour MP for Leeds Central and Headingley, is leading calls among backbenchers to establish a national commission on reforming the voting system.

He has tabled an amendment to the Representation of the People Bill, which will be debated in the Commons on Wednesday, calling for the Government to back the move.

Mr Burnham on Tuesday suggested he was open to the idea of electoral reform, but told the Commons that “we will need to get a consensus at the next election” to make such a change.

Veteran Labour MP Dame Emily Thornberry has meanwhile pressed the Prime Minister to back her amendment to the Bill which would ban “overseas voters” from financially backing political parties.

The Prime Minister was reported to have steered away from plans for a £500,000 cap on all political donations in the summer, amid concern about its impact on Labour’s trade union backers.