The National Railway Museum is at the centre of a nepotism row after the husband of one of its curators was awarded two contracts without facing a competitive tender.
Adrian Ashby, the husband of Helen Ashby, the museum's head of knowledge and collections, received about £25,000 for work including painting an engine, both as a contract worker and through the York-based museum’s official payroll.
The museum is part of the Science Museum Group and is classed as an exempt charity.
Ashby also received a contract to help restore the famous Flying Scotsman engine as well as nearly £16,000 for work involving driving an engine during the museum’s stage production of The Railway Children.
The allegations were revealed in a Yorkshire Post investigation.
Prospect, a trade union that represents staff at the NRM, has now called for an investigation into how the contracts were awarded.
Andy Bye, negotiations officer at Prospect, said: "There ought to be an inquiry led by the trustees to ensure public money is being spent correctly and fairly.
"No one should be given an advantage and the trustees need to be sure there has been equality of opportunity in relation to all the work provided to Mr Ashby."
The NRM denied any suggestion of nepotism and said that Mrs Ashby was not involved in the decision to award her husband contract or payroll work at the museum.
The museum said it normally used proper tender processes when deciding to award contracts and that Ashby had been awarded only seven out of 40 painting contracts in the past five years.
But the museum admitted that it had not used the tender process on two occasions relating to Ashby because it was necessary to carry out the work quickly and he was available at short notice.
Ashby was "trained and qualified to drive the 08 shunter" for his work in The Railway Children, the museum said, which was why he was awarded this contract.
Steve Davies, director of the NRM, said: "Adrian has been a volunteer at the museum for more than 35 years and has an excellent track record of delivering high-quality work, both as a volunteer and in a paid capacity."
Science Museum Group said in a statement that it "takes these matters very seriously and will review whether an internal investigation is required by 31 August".