Labour has slammed the brakes on its flagship pledge to spend £28billion-a-year on investing in green energy projects.
In a major shift, Shadow Chancellor Rachel Reeves admitted the 2021 commitment might not be reached until the "second half of the first Parliament" if Labour won the next election.
The plan, announced in 2021, was to be funded from borrowing, and spent on green projects like offshore wind farms and developing batteries for electric vehicles.
Ms Reeves said the party would "ramp up" investment over time but said the economic carnage inflicted on Britain by Liz Truss had narrowed Labour's options.
"The truth is I didn't foresee what the Conservatives would do to our economy - maybe that was foolish of me," she told BBC Radio 4's Today programme.
Ms Reeves said it was important not to be "reckless" with spending, and "economic stability and financial security has to come first" amid price rises and interest rate hikes for Brits.
It comes after speculation over tensions within the party over the pledge in the run up to the election amid growing attacks from Government ministers.
Keir Starmer is expected to unveil more details of his mission to make Britain a clean energy superpower later this month.
Ms Reeves said: "The thing that is really important to ensure that we meet our fiscal rules because they are so important.
"We saw what happened just last year when the Conservatives embarked on this mini Budget of a load of unfunded commitments, that crashed the markets and has resulted in that Tory mortgage penalty that we are all paying.
"So we will ramp up to the £28 billion investment in the opportunities of the industries of the future and to reduce bills."
Asked if Labour would borrow at all in its first year for the plan, Ms Reeves refused to give a rough number.
"We haven't had the final set of numbers by the Government so we're not going to give our final set of numbers," she said.
"The truth is I didn't foresee what the Conservatives would do to our economy - maybe that was foolish of me.
"But I did not envisage the mini Budget that crashed our economy, pushed up interest rates in this way.
"So I'm not going to give you a number when I don't know what more damage the Conservatives are going to do."
Ms Reeves insisted that Shadow Climate Change Secretary Ed Miliband was "on the same page" as her.
She said: "Keir, Ed and me are all on the same page on this. We know that unless we have this green prosperity plan those jobs and investments will go elsewhere, but that everything we do must rest on these pillars of economic responsibility and fiscal responsibility".
Mr Starmer said the plan would be "Britain’s ticket to better jobs, lower bills and a brighter future.
However he added: "But I’ve always said that Labour will always be responsible with the public finances. That means dealing with the ruinous Tory handling of the economy."
Left-wing activist group Momentum said it was "a hugely disappointing step backwards from the Labour Leadership".
A spokesperson said: "We will never tackle the climate & social emergencies before us if we water down our policies at the first sign of attacks by the Tories & right-wing press."
Jess Ralston, head of energy at the Energy and Climate Intelligence Unit (ECIU), said: "Since the Inflation Reduction Act was passed nearly a year ago, spades have hit the ground in the US, but the UK's been stuck in the mud.
"Whichever party is in charge in the coming years will have to prove why organisations should invest here compared to the US or EU, and with the global race heating up, there's really no time to lose."
Mr Miliband sought to dampen speculation of tensions at the top of Labour - and insisted it wasn't being abandoned.
"We can't pretend those aren't constraints," he told BBC Radio 4's World At One programme.
"Some people in the Conservative Party say we should abandon our plan. We are 100% saying today we are not abandoning our plan. We are sticking with it and we're showing how we're going to deliver it."
Chancellor Jeremy Hunt weighed into the row, claiming the plan would add tens of billions of pounds to the national debt.
He said: "This superficial change from Rachel Reeves still adds around £100billion to our national debt - meaning higher mortgages for families and higher debt interest bills for taxpayers.
"A responsible approach should tackle inflation, not fuel it…"
It comes as the Government announced it will remove the windfall tax on oil and gas companies should the price of the commodities continue to fall.
Ministers said that they would slash the current 75% tax on North Sea oil and gas profits back to its regular 40% if prices reach certain levels.
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