The UK government and the monarchy’s land and property business will join forces to attract investment in new a publicly-owned energy firm, Labour has said.

It wants the Crown Estate, which owns much of the seabed around the UK, to help push forward offshore windfarm projects as part of its plans for GB Energy.

Labour said it will invest £8.3bn in the Scotland-based company, partly funded by a North Sea oil and gas windfall tax, and create it with the passing of a law.

However, the Conservatives have said GB Energy is “nothing but a gimmick that will end up costing families”.

Labour’s hope is that GB Energy, a key manifesto pledge, will reduce UK “over-reliance” on fossil fuel markets, with prices rising rapidly after Russia’s invasion of Ukraine.

This is turn pushed up the pace of general price rises, contributing to the cost-of-living crisis.

GB Energy will be “at the heart of the government’s mission to make Britain a clean energy superpower”, the government said.

It added that the company will take stakes in energy projects to help speed them up.

This includes giving a boost to technologies including carbon capture and storage, which has yet to be deployed at scale, along with hydrogen, wave and tidal energy.

Eventually, GB Energy may take a controlling interest in some renewables generation projects.

The partnership with the Crown Estate will mainly focus on offshore wind projects.

It will lead to between 20GW and 30GW of new offshore wind reaching seabed lease stage by 2030, the government said.

The Crown Estate already had this as a target, but on Thursday the government confirmed it will help.

The agreement is only for projects around England and Wales, but the UK government is also in discussions with the Scottish Government and Crown Estate Scotland on support for Scottish projects.

With GB Energy’s £8.3bn of funding, Labour hopes to attract £60bn of investment.

Prime Minister Keir Starmer said that the plans were “turbocharging our country toward energy security”, and promised that it would lower energy bills.

However, the Conservatives have said GB Energy “will end up costing families, not cutting bills”.

“Labour have already been forced to admit that their flagship energy company won’t generate any energy, and now we know it’s a financial black hole – funnelling taxpayer’s money into reducing risk for multi-million-pound energy companies,” said shadow energy secretary Claire Coutinho.

The government wants GB Energy to speed up renewable energy projects by helping them develop, and invest in them alongside private investors.

It wants it to work with local energy projects and the nuclear industry.

Alongside a new law to create GB Energy, the government will also loosen regulation on the Crown Estate so it can invest and borrow more.

The government has taken a number of decisions on renewables generation since coming to power in the recent election.

It has approved three big onshore solar farm projects which have faced local opposition.

Energy Secretary Ed Miliband has also scrapped a de facto ban on onshore wind developments.