The government will come under fire tomorrow from a renewable energy sector increasingly concerned about potential delays in the implementation of a “feed-in tariff” meant to kickstart a domestic green power revolution.

David Kidney, an energy minister, will be questioned at a summit in London organised by Renewables UK, formerly the British Wind Energy Association, over its failure to pass a statutory instrument needed for the introduction of the tariff.

The power companies told the Department of Energy and Climate Change (DECC) that it should introduce the legislation before Christmas if they were to be ready to start the clean energy scheme by the agreed date of 1 April. The statutory instrument giving energy regulator Ofgem the power to introduce the tariff at the start of next month has still not been laid in front of parliament, despite needing a 21-day lead-in time for it to become active.

“The government has basically got a narrowing window of 10 days now,” said one key industry figure, who asked not to be named. “DECC officials are being given a hard time about the continuing delays.”

A spokeswoman for DECC denied there was any threat to the tariff's start date, saying it remained committed to 1 April, while Ofgem said it was doing all it could to ensure the tariff was introduced on time. An Ofgem spokesman said: “We will ensure that all the core functions are in place for administering the scheme for when we go live on 1 April.” Asked what would happen if the relevant law was not in place for the regulator to carry out its role, the spokesman replied: “That is a question you must ask DECC.”