Environmental group Friends of the Earth (FoE) has questioned the legality of the consultation period established by the Department for Energy and Climate Change (DECC) for its proposals to close Renewable Obligation subsidies a year earlier than planned.

In a letter addressed to secretary of state Amber Rudd, FoE legal adviser Jake White has called upon the department to extend its consultation period by the minimum of four weeks, suggesting DECC might have breached the government’s own consultation guidelines.

Last week DECC confirmed its intention to close RO funding for sub-5MW projects as of 1 April 2016 and opened a public consultation for comments which is currently due to end of 2 September.

But FoE argue that in setting such a short timeframe for commentary, DECC could be in breach of administrative law owing to so-called ‘Gunning Principles’ which set out acceptable standards for public consultations.

The Gunning Principles set our four basic requirements that are essential for all public consultations, the third of which states that “adequate time must be given for consideration and response”.

The Principles were then amplified by a further Supreme Court ruling which stated that any demand for fairness is likely to be “somewhat higher” if an authority proposes changes “depriving someone of an existing benefit or advantage”.

FoE has argued that withdrawing RO support a year earlier than planned, coupled with the removal of grandfathering rights, constitutes such a benefit and DECC would therefore be required to grant an extended consultation period in the matter of fairness.

The group has also raised concerns that the consultation period has been scheduled to start and end during the traditional summer period – a matter also raised by Energy and Climate Change Select Committee chair Angus MacNeil last week – is also unfair on those who would ordinarily respond.

White’s letter points out that government’s own guidelines state: “where the consultation spans all or part of a holiday period policy makers should consider what if any impact there may be and take appropriate mitigating action”.

FoE renewables campaigner Alasdair Cameron said DECC’s approach to the consultation was “undemocratic” and an attempt to “sneak through this rushed consultation while everyone is on holiday”.

“Ministers’ justification for the approach on grounds of urgency makes no sense when the changes decided by the consultation will be backdated to apply from 22 July, regardless of when it ends.

“Government policy is now actively holding back decarbonisation, and hitting community solar schemes, solar schools and small businesses hardest. If the Prime Minister is going to have any credibility at the climate talks in Paris he needs to stop treating renewable energy as something he can just pick up or throw away for a few headlines,” Cameron added.

When contacted on the matter, a DECC spokesman insisted to Solar Power Portal that the consultation remained within recommended guidelines and claimed changes to renewable subsidies were a manifesto commitment.