An influential group of MPs has said that Labour needs an urgent renewal of economic strategy to offer voters “more than better management of decline” before the next general election.

With Keir Starmer fighting to ward off a leadership challenge, the leading backbenchers from the soft-left Tribune group published a series of essays calling for bolder action to salvage its remaining time in power.

In a foreword by the former cabinet minister Louise Haigh, and Yuan Yang, a prominent figure from Labour’s 2024 intake, the MPs issued a thinly disguised attack on Starmer amid pressure on him to set out a timeline for his departure.

“We do not present this as the final word. They are an invitation – to challenge assumptions, test ideas, and help build a broader coalition for economic renewal. Because the economic status quo is no longer defensible,” the MPs wrote.

“And if politics is to regain trust, it must offer more than better management of decline.”

Calling for higher taxes on wealth, action on the cost of living crisis, and more borrowing to fund investment – including a redrawing of the government’s fiscal rules – the group said the essays were intended as “idea generation” rather than a manifesto for a Starmer replacement.

However, amid febrile conditions within party ranks after crushing defeats in local elections across Britain last week, several MPs loyal to No 10 and groups linked to the prime minister’s rivals are increasingly floating new ideas in public to push for a change of direction.

Haigh, who quit in the early months of Starmer’s government after it emerged she had been convicted of fraud over a missing work phone, is seen as a key power broker on the left of the party for any would-be replacement, and became one of the first senior figures to call openly for his resignation.

In her contribution Haigh called on Labour to replace Rachel Reeves’s fiscal rules with a requirement to target lower levels of debt over 10 years rather than five to allow for a more flexible approach to investment.

However, in a nod to pressure from bond market investors fretting over higher borrowing levels and a leftward shift in policy, she said this should only be done after the government had balanced day-to-day spending with tax receipts.

Haigh also called for the scrapping of stamp duty and its replacement with a proportional property tax and reformed council tax, higher rates of capital gains tax, and for the breakup of the Treasury – handing its budget-setting powers to No 10, while turning it into a new growth ministry.

Yang, a member of the Treasury committee, urged Labour to use its response to the Iran war to overhaul cost of living support, including proposing a free minimum energy guarantee modelled on a system in Austria, further cuts to green and social levies on energy bills, and free bus fares for under-25s and recipients of universal credit.

The prime minister vowed on Monday to prove his doubters wrong in a make-or-break speech. However, more than 70 Labour MPs – including Yang – have now urged him to set out a timetable for his departure.

Labour MPs have said they believe the health secretary, Wes Streeting, could imminently launch a challenge. Andy Burnham, the mayor of Greater Manchester, is also hoping to find a route to parliament to seek the leadership.

In a wide-ranging pamphlet, the essay collection was published in the quarterly Renewal political journal, overseen by the progressive left thinktank Compass – led by Neal Lawson, a prominent supporter of Burnham.

However, the Tribune group insisted they had long planned to publish the essay collection, had contributed independently, and wanted to “focus on ideas not individuals”.

Yang, who is a member of Tribune and the Labour Growth Group, a faction once considered loyal to Starmer, said: “You can see our constituents are clearly dissatisfied with the economic outcomes. So it is time for us to dig into the reasons behind that and to think about the whole structure of the economy.”