A total 42,090 measures were been installed under Eco during April, down from 95,388 in the previous month.
The Department of Energy and Climate change (Decc) said this was likely to be in response to the incentives for energy companies to deliver Carbon Saving Target (CERO) measures by the end of March 2014.
The total number of Eco measures installed by the end of April was 818,701.
Just over a third (36 per cent) of these measures were cavity wall insulation installations, 29 per cent were boiler upgrades, 21 per cent were loft insulation measures, and seven per cent was made up by solid wall insulation installations.
The government figures also showed that 23,811 assessments were completed in May – up from was the 22,005 in April – bringing the number of overall Green Deal assessments up to 234,050.
There were 389 new Green Deal plans in progress at the end of May, bringing the total up to 2,828.
Of the plans agreed, 863 were new (quote accepted), 593 were pending (plan signed), and 1,372 were live (measures installed).
In its first week, the Green Deal Home Improvement Fund received a total of 1,736 applications for more than £2.6 million of money towards energy efficiency improvements.
An estimated £6.4 million was claimed back via Green Deal cashback by the end of May, with 15,100 vouchers being issued, of which 12,251 were claimed with the majority going towards boiler replacements.
Climate change minister Greg Barker said: “It’s great that May was such a successful month for the Green Deal with 23,811 assessments carried out – the second highest rate ever.
“And it’s even more encouraging that 76 per cent of people who’ve had a Green Deal assessment are taking action.”