Energy firms will be given the long-awaited confirmation about how much they will be guaranteed by the government for the electricity they generate in a move it is hoped will push forward East Anglian wind farm plans.

A renewables strike price will be unveiled by chief secretary to the treasury Danny Alexander this morning following months of negotiations between energy firms and the government.

Ministers will announce that they will cut support for onshore wind and solar energy, but give more backing to offshore wind power.

Earlier this year ministers unveiled plans for the guaranteed prices that will be paid for electricity from renewables including offshore and onshore wind in the coming decade, in order to give investors certainty of the return they will get to cover high capital costs.

But the draft prices only ran up until 2020 and business leaders have been arguing that the large sums of money and long timescales of projects mean that they need certainty for far longer.

The set prices for onshore wind power and solar energy will be cut from 2015, while those for offshore wind power will be increased.

Norfolk is set to benefit from a number of proposed wind farms, including the Triton Knoll project, co-ordinated by RWE Npower Renewables, which has plans to build 228 wind turbines 25 miles off the coast of north Norfolk.

Simon Gray, chief executive of the East of England Energy Group (EEEGR), the business-led regional alliance which aims to drive growth in the energy sector, said: 'I am hoping it will be of the right order to maintain impetus for the industry. Everything has gone back by certainly two, in some cases even five, years in terms of where we thought we would be now.

'Some companies which set themselves up to capitalise on the burgeoning offshore wind industry have gone to the wall because of the lack of government plans.

'What it will mean is at last some stability for the industry and we can see some light at the end of the tunnel and start planning the scaling up of activity for these developments.'

It will be part of a number of announcements in the new national infrastructure plan (NIP) setting out over £375bn of planned public and private investments to 2030 and beyond.

The government will sell its 40pc stake in Eurostar as part of a plan to privatise £20bn of financial and corporate assets by 2020.

Ministers have been given a boost by major insurers, who have announced plans to invest £25bn in UK infrastructure projects over the next five years.

The plans set out today include a new target for selling off financial assets, doubling the amount from £10bn to £20bn including the shareholding in the cross-channel train operator. Last month Eurostar revealed it had seen an increase in revenues and passenger numbers compared with last summer.

Other measures being announced include:

A further £50m will be allocated to redevelop the railway station at Gatwick Airport.

A government guarantee could support finance for the development of a new nuclear power station at Wylfa on Anglesey.

The £1bn Northern Line extension to Battersea in south-west London will also be guaranteed by the government.

A £10m competitive fund will open in early 2014 to test ways to deliver superfast broadband to remote areas of the UK.

The planned infrastructure investment has increased from £309bn last year to more than £375bn, with 291 of the 646 projects and programmes already under construction.

Mr Alexander will say: 'The announcement today that six major insurers will invest £25bn over the next five years is a massive vote of confidence in the UK economy.

'It supports the wider £100bn public investment to rebuild Britain over the next seven years that I announced at the Spending Round 2013. Underground, overground, onshore, offshore, wired or wireless, tarmac or train track. You name it, we're building it right now.

'This is great news for the people of the UK because after years of neglect, the UK's energy, road, rail, flood defence, communications and water infrastructure needs renewal.'