Such decisions usually need to be announced before politicians in Parliament. But since it begins its summer break today that is now impossible. The Department for Energy and Climate Change confirmed the delay, but would not give a reason.
"We'll bring forward the proposals in due course as the details are still being finalised," a spokesman for the department said. But he added that it was possible that the decision could be made over the summer.
"Obviously we like to do things in the proper way, but this is obviously important to investors so if required, I'm sure we could do it without having to go to Parliament."
DECC originally proposed cutting the RO for onshore wind by 10% last October. But the level of RO has become extremely politicised in recent months, particularly for onshore wind.
In February, over 100 Conservative MPs wrote to prime minister David Cameron demanding that subsidies for onshore wind be cut further. Chancellor George Osborne was reportedly considering a 25% cut.
Maf Smith, deputy chief executive of trade body RenewableUK said that there was no case for a further cut in the support for onshore wind. "Any further delay in an announcement will of course have an impact on investor confidence and on the deployment of wind energy," he said.
The new banding levels are due to come into force in April 2013.