Labour would invest GBP28bn a year in climate measures to protect Britain from disaster, Rachel Reeves has announced in by far the party’s biggest spending pledge to date.

The amount would quadruple the government’s current capital investment, and Labour said it would hope to attract a matching sum of private investment in green technologies. In total, the party will commit to spending GBP224bn on climate measures over the next eight years.

Reeves, the shadow chancellor who has stressed the party’s commitment to fiscal responsibility, told Labour’s conference in Brighton she would be “the first green chancellor” and that the costs of climate change would be greater if the government did not invest now.

The party is pledging an additional GBP28bn of green capital investment a year until 2030 – equivalent to more than half the current defence budget. Under Labour, Reeves said, there would “no dither, no delay” in tackling the crisis.

Targets for spending would include gigafactories to build batteries for electric vehicles, the hydrogen industry, offshore wind turbines manufactured in Britain and more everyday infrastructure such as home insulation, cycle paths, tree planting and flood defences.

Labour said the public spending was justified to prevent costs spiralling further, quoting the Office for Budget Responsibility’s 2021 fiscal risks report, which said delaying significant investment by a decade could double the costs of a green transition.

Reeves and the Labour leader, Keir Starmer, will hope the policy provides a definitive answer for swathes of the membership who feel the party has been insufficiently bold in tackling the climate crisis. On Sunday, Starmer was chased by Labour activists from the campaign group Green New Deal Rising, calling for GBP85bn of infrastructure investment to create green jobs.

“Value for money means knowing when and where not to spend,” Reeves told the conference hall. “But it also means knowing when and where to invest – to prevent far greater costs further down the line.

“There is no better example of this than in the case of climate breakdown. As chancellor I will not shirk our responsibility to future generations and to workers and businesses in Britain … We will provide certainty and show leadership in this decisive decade. I will be a responsible chancellor. I will be Britain’s first green chancellor.”

The announcement came amid a split in Starmer’s shadow cabinet over nationalising energy companies. Reeves and Starmer have said it is not on Labour’s agenda, opening up a divide with the shadow business secretary, Ed Miliband, who wanted to keep the option open.

On Sunday, Labour delegates passed a motion calling for a “socialist green new deal” including the nationalisation of the energy sector and the creation of a national nature service, “a government programme creating millions of well-paid, unionised green jobs with publicly owned entities” and “mass investment in green technologies and renewables”.

Asked about Starmer’s pledge when he was standing to be Labour leader to put energy companies into “common ownership”, Reeves told the BBC earlier on Monday that the fuel crisis was “not because of nationalisation or privatisation”.

Reeves called for more government action to bring in HGV drivers amid the petrol shortages.

“We’ve got to plug those gaps,” she said. “We’ve been saying for quite a while now that the government should refer this to the migration advisory committee about skill shortages. But then, they need to be training up more British workers to have the skills to be able to do these jobs, and improve particularly the conditions, and also the pay, for HGV drivers.”

Asked whether the crisis was a consequence of Brexit, Reeves said Labour had always noted “a number of gaps in the deal” signed by Boris Johnson but would only seek solutions to bring in outside workers as needed, not a more general return to the free movement of people.