A legal challenge has been launched over the deal that gave the BBC responsibility for funding free TV licences for the over-75s.
The National Union of Journalists said the decision was in breach of public sector equality, unlawfully discriminated against persons under the age of 75, and was in breach of the BBC's rules of governance.
The union's general secretary, Michelle Stanistreet, said: "We have already said this was a shabby deal which is not good news for the licence fee payer or the BBC staff.
"It places the corporation in a situation where more cuts to jobs and programming are needed because of the funding shortfall, a move which will inevitably compromise quality.
"As well as being a bad deal done without any engagement with licence fee payers, we also believe that it is legally flawed and our legal team has written to the BBC Trust asking a series of questions and requesting it to reverse its decision to agree to pay for the licences of those aged 75 and over."
The BBC Trust said: "We have received the letter and will respond in due course."