Labour is facing criticism after it ditched its pledge to spend £28 billion a year on green projects, as senior party figures sought to defend the U-turn.
Environmental groups, trade union allies and energy industry figures have all expressed disappointment at the move – while the Tories have continued to attack Labour’s fiscal credibility.
Sir Keir Starmer announced on Thursday the figure would be drastically scaled back to £23.7 billion over the course of the next parliament if his party wins the next election.
He insisted the ambitions behind Labour’s flagship green prosperity plan remain the same, and recommitted to his mission to achieve clean power by 2030.
But the party’s plan to insulate homes is set to be one casualty of the climbdown, with five million expected to be completed in the first five years rather than the 19 million initially promised.
She said: “I’ll make no apologies for ensuring that our plan is fully costed, fully funded and deliverable within the inheritance we’re going to get.
“It is going to be a bleak inheritance after the damage the Conservatives have done to our economy.”
She said: “In the almost three years that I’ve been shadow chancellor, I think people have heard loud and clear from me that fiscal responsibility, economic responsibility, are the most important things for me because it is absolutely essential that the public finances are managed well.”
“And when economic circumstances change, your plans have to change as well,” Ms Reeves added.
Speaking to Sky News, shadow business secretary Jonathan Reynolds insisted the plan was still ambitious.
“If the cost of borrowing has gone up at the rate it has, we have to reflect that.
“I’d love it to be different but we have to be honest and candid about the impact it has.”
Concerns have been expressed by some Labour MPs on the left of the party, including Clive Lewis and Barry Gardiner, while the Unite union – a major party donor – said the party risks “outsourcing their policy-making to the Conservatives”.
Emma Pinchbeck, chief executive of trade association Energy UK, also warned that “business needs to know that politicians won’t pull the rug from under them”.
Those attacks continued in the wake of the announcement, with Mr Sunak mocked the Labour U-turn during a visit to the South West.
The Prime Minister told broadcasters: “I think what Labour announced yesterday just demonstrates what we’ve been saying – they absolutely don’t have a plan.
“Their signature economic policy is in tatters, and when you don’t have a plan, you can’t deliver any change for the country.”