The You Forgot The Birds campaign, which includes the former England cricketer Sir Ian Botham, has conducted a study into the charity’s annual account and found that the charity spent 24 per cent (£30m) of its £122m income on conservation work in 2012/2013.
The campaign claims that the RSPB spends 26 per cent of its income on fundraising, 40 per cent on research, education, political lobbying and public relations and 10 per cent on administration.
The group says that the RSPB has failed to live up to the promise it makes to members that 90p in every pound goes directly towards its conservation work.
Botham, who runs his own commercial shoot, said in a statement on the You Forgot the Birds website: "If the RSPB was really committed to its slogan of ‘Giving Nature a Home’, it would spend a lot more than 24 per cent of its income on running nature reserves. It’s a massive bureaucracy where donations are spent on homes for office workers not homes for birds."
Grahame Madge, a spokesman for the RSPB, said that the study was very misleading. He said: "It’s very naive to suggest that the only money we spend on conservation work is the 24 per cent spent on our nature reserves. It completely ignores the money we spend on our marine work, for example."
He said that those behind the You Forgot The Birds campaign were trying to protect their own interests. "When you look at those behind the campaign, they all have associations with field sports and shooting," he said. "We have grave concerns about birds of prey being shot and poisoned and some of the practices on land used for grouse shooting."
The commission confirmed that it had received a complaint about the RSPB. A spokeswoman for the commission said in a statement: "We will assess the concerns to determine what, if any, regulatory concern there might be for us."
She added that it was not formally investigating the charity.