Nearly 620 miles (1,000 km) of new power lines need to be built to meet the government’s clean energy plans, official energy planners have concluded.

In a report, the body responsible for connecting new projects to the grid said Labour’s target to decarbonise electricity by 2030 was “achievable” but a “huge challenge”.

It will warn that infrastructure for the electricity grid will need to be built much faster than it has been in the past decade to meet the commitment.

Energy Secretary Ed Miliband said ministers had committed to “significant reforms” to the planning system to speed up new connections.

Miliband has called on the National Energy System Operator (NESO) to review ministers’ clean energy plans after Labor is returned to power in July’s general election.

The utility was originally owned by National Grid, a private company, but was transferred to government ownership last month.

The government is due to publish its action plan to modernize the network in the coming months.

Government sources see his report, to be published on Tuesday, as a vindication of his pledge to deliver a zero-carbon electricity system in Britain by 2030, a key part of Labour’s election manifesto.

But it also highlights the scale of the task when it comes to increasing the supply of renewable energy and connecting it to the grid.

Meeting the pledge, it believes, would require a significant increase in offshore wind capacity, alongside increased electrification of heat, transport and industry.

Nearly 1,000 km (620 miles) of new power lines would be needed to connect the new renewable energy to the grid, along with 4,800 km of undersea cables, the statement said.

The report points out that this would more than double in five years what has been built in total in the last 10, requiring many projects to start construction in the next 6 months to two years.

It added that this “challenging” timeframe will require changes to the planning system to reduce the time it takes for new projects to gain approval.

The construction of hundreds of miles of new pylons is also likely to face political opposition, with a number of schemes facing fierce local opposition.

The previous Conservative government has signaled it is open to the idea of making cash payments households in the path of large new electricity pylons, alongside existing community compensation schemes paid through consumer bills.

The 2030 target is five years ahead of what the Conservatives promised before the election, with Claire Coutinho, shadow energy secretary under Rishi Sunak, calling it “unrealistic” and “purely ideological”.

There was also some skepticism within the trade union movement about the potential impact on jobs.

The GMB union, which represents oil and gas workers and donates to Labour, said any government plan to boost wind and solar power should come with “an ironclad commitment to deliver quality jobs here”.

The NESO report estimated that the 2030 clean energy plan would require an average of £40bn of investment per year, most of it from the private sector, requiring a significant boost from current levels.

It did not model the impact of its plan on consumer bills “given the heavy reliance on political elections.”

But it argued that the additional costs to consumers, such as the long-term fixed prices they have to pay for renewable projects, would not be higher than they would have been otherwise, thanks to the savings in annual running costs from having to use more little natural gas.

It also said the 2030 target would depend on a four- to five-fold expansion of its demand-side flexibility service, which encourages households and businesses to save money by using less electricity during peak periods.

The authority will also begin consulting on plans to a system review for connecting new renewable power plants to the grid, to prioritize projects that are ready to be built.

Currently, some projects can face wait times stretching into the next decade to connect.