Friends of the Earth has warned the government could face legal challenges if it cuts feed-in tariffs in tomorrow's Comprehensive Spending Review.

The government could face a legal challenge if tariffs paid to homes, businesses and communities for generating small-scale renewable electricity are cut in tomorrow's Comprehensive Spending Review, Friends of the Earth has warned.

In a letter sent to Energy Minister Greg Barker, the environmental campaigning charity points out that feed-in tariff levels have been set out by the government, with a clear statement that they will not be reviewed – let alone reduced – until 2013.

Friends of the Earth warns that any change to tariff levels before this review could lead to a legal challenge from councils, community groups or small-scale energy producers who have planned and invested in renewable electricity infrastructure expecting that published tariff levels will not change. According to recent reports, feed-in tariffs could be cut by 10%.

Friends of the Earth's policy and campaigns director, Craig Bennett, said: "If Ministers try to cut agreed payments for green electricity generation they may find themselves in court.

"The government has clearly set out tariff levels for the first three years of the scheme, and councils, community groups and businesses have planned and invested accordingly. Reviewing tariff rates could undermine these plans.

"Cutting feed-in tariff levels would risk destabilising the UK's small-scale renewable electricity market at the precise moment that it is finally starting to gain momentum, as well as undermining David Cameron's promise to lead the greenest government ever."

Wolseley's Neil Schofield recently said that feed-in tariffs were "distorting the market" for solar technology.