The Labour Party’s plans to nationalise the country’s energy networks would hinder the shift to green energy, National Grid has said.
The firm is the UK’s largest transmitter of electricity and gas via its network of pylons and pipelines.
Labour said its pledge to return it to public ownership would “usher in a Green Industrial Revolution” and tackle climate change.
National Grid said the proposal was the “last thing” that was needed.
The Labour proposals are contained in a document entitled Bringing Energy Home, due to be presented on Thursday by leader Jeremy Corbyn and Rebecca Long Bailey, shadow energy secretary.
It says Labour plans to fit solar panels to one million social and low income homes to tackle fuel poverty, providing households with free energy and average savings of £117 a year.
Those savings would rise to £270 for households with retired people.
“Any unused electricity generated by the programme will be used by the National Grid, which Labour will take into public ownership, raising an additional £66m per year for local authorities,” the party said.
However, after the report was leaked, National Grid said: “These proposals for state ownership of the energy networks would only serve to delay the huge amount of progress and investment that is already helping to make this country a leader in the move to green energy.
“At a time when there is increased urgency to meet the challenges of climate change, the last thing that is needed is the enormous distraction, cost and complexity contained in these plans.”
Labour said it had committed to generating at least 60% of the UK’s electricity and heat from renewable and low-carbon sources by 2030.
It would take the four licensed and regulated electricity and gas transmission companies, including National Grid Electricity and National Grid Gas, back into public ownership and “replace existing private monopolies with publicly owned and locally run institutions”.
“These two policies are part of Labour’s plans to usher in a Green Industrial Revolution in housing, transport and industry – creating over 400,000 jobs and tackling climate change,” Labour said.
Mr Corbyn said: “In this country, too often people are made to feel like the cost of saving the planet falls on them. Too many think of green measures as just another way for companies or the government to get money out of them, while the rich fly about in private jets and heat their empty mansions.
“Labour’s approach is different. Our Green Industrial Revolution will benefit working-class people with cheaper energy bills, more rewarding well-paid jobs, and new industries to revive the parts of our country that have been held back for far too long.”
This is not the first time National Grid has hit out at Labour plans to nationalise the energy network.
In 2017 the party’s manifesto committed it to “take energy back into public ownership to deliver renewable energy, affordability for consumers, and democratic control”, prompting the company’s boss to tell the Guardian newspaper: “Clearly we do not think it is a good idea.”
The Conservative’s vice chairman for policy, Chris Philp, said Labour’s “ideological plan for the state to seize these companies would cost an eye-watering £100bn and saddle taxpayers with their debts”.
“It would leave politicians in Westminster in charge of keeping the lights on and leave customers with nowhere else to turn.
“With no credible plan for how Labour would pay for this, more borrowing and tax hikes would be inevitable.
“Through measures like our energy price cap, the Conservative government will continue to protect people from unfair bill rises while increasing renewable electricity to a record high.”