The number of Green Deal assessments carried out in April rose 28 percent to 9,522, the Government has said. Since the launch, 18,816 assessments have been made.

The figures also showed a slower pickup in the number of businesses registering for the programme, with 55 authorised Green Deal providers, up from 48 the previous month. The number of installers rose from 831 at the end of March to 942.

Richard Griffiths, policy and campaigns consultant at the UK Green Building Council, said: “As we saw a month ago, the number of Green Deal assessments continues to grow and that is encouraging. But we are now reaching the point where we must surely start to see a significant number of these turn into Green Deal plans. Early reports suggest that this is starting to happen, but not yet at a rate commensurate with the challenge we face in retrofitting the UK’s homes.

“The real test will come in a couple of months’ time, when the DECC-funded assessments have worked through the system. Will the rate of assessments we have seen so far be maintained, and can we be hopeful that a reasonable proportion of those who received free assessments will turn out to be genuinely serious customers for the scheme?

“If the answer turns out to be “no” to either of these questions, the Government should commit to acting on the lessons learned from the first six months and step in to introduce measures to drive demand for retrofit.”