The visit to Holyhead, which also involved Jo Stevens, the shadow Wales secretary, was to promote a remaining element of the scaled-back green plan, GB Energy, a publicly owned sustainable energy company.

Part of this would involve floating offshore windfarms, which Starmer said would not just make energy more sustainable but would also bring down bills.

“Floating offshore wind is going to be a gamechanger when it comes to energy,” he told BBC Wales. “Some country in the world is going to be the leader, and I want that to be the UK. What we can do is have the Westminster government, and the Labour government here in Wales, working on the next generation of energy.”

Speaking to ITV Wales, Starmer said last month’s decision to slash the pledge to invest £28bn a year in green policies to under £15bn still left “a huge difference” with government policy over renewables.

Interviewed by BBC Radio 4’s World at One, Miliband, who has been largely quiet since the change of policy, said there were “huge opportunities” for jobs from renewable energy, and that the floating windfarm plan was a major policy.

“It’s going to be the first priority of GB Energy’s £5bn investment,” he said. “It will partner with the private sector in places like north Wales so that we can get the jobs that floating wind can bring and, indeed, the lower energy bills.”