The UK’s latest renewable energy auction round has been delayed by a legal challenge, throwing a spanner in the works of a process designed to award up to 6GW of new capacity and expected to be dominated by offshore wind.

The UK Department of Business, Energy and Industrial Strategy (BEIS) confirmed that the bidding window for the contract-for-difference (CfD) round has been pushed back to 29 August from an original deadline at the end of this week.

The department gave no further details of the nature of the challenge and parties involved are prevented from commenting publicly by competition rules, but reports suggested an application has been lodged for a judicial review.

BEIS said: “Our Contracts for Difference scheme has supported the investment of £490m annually in renewable technologies and more than 50% of our energy now comes from low-carbon sources, a vital part of our move to becoming a net zero emissions economy by 2050. We run the scheme lawfully and will be contesting this claim.”

The delay to the sealed bidding window is likely to have a knock-on impact to the announcement of results, currently scheduled for early September.

The latest auction aims to contract up to 6GW of capacity and follows a plunge in costs to as low as £57.50/MWh over two rounds in 2015 and 2017.

For the first time, ‘remote island’ onshore wind farms will be eligible to take part and compete with offshore wind projects.

Luke Clark, head of external affairs for industry body RenewableUK, said: “We’re confident that the upcoming Contracts for Difference auction will deliver record new capacity at record low prices.

“The auction is a competitive process and firms in the sector understand that dates can change for different steps in the process. We want to see the CfD auction concluded as quickly as possible so that companies can move ahead with billions of pounds of new investment in UK infrastructure, and the Government is committed to awarding new contracts next month.”