Rat droppings have been found in the kitchen of an East Coast mainline train.
The RMT union said the droppings – found on a Virgin Trains East Coast service (VTEC) – presented a risk to staff and passengers.
The rail union has accused the operator of showing a “shocking attitude to hygiene and health”.
Virgin Trains East Coast said it was an isolated incident, and the area was cleaned before being put back into use.
RMT General Secretary Mick Cash described it as a “major hygiene issue” affecting both staff and passengers.
He said: “It is frankly appalling that VTEC, an alliance of Stagecoach and Virgin, has allowed this rodent scandal to fester on their trains regardless of the risks to staff and passengers alike.
“RMT is demanding urgent action over the rodent infestation.
“Passengers paying through the nose to travel on these trains will also be rightly angry to hear about VTEC’s shocking attitude to hygiene and health and safety.”
Pictures of the droppings were taken on a London to Edinburgh service earlier this week, the RMT said.
A spokesman for Virgin Trains on the east coast route said: “This was an isolated incident which we believe was caused by a supplier.
“As soon as we became aware of this, we quickly acted to isolate the affected areas. These areas were then thoroughly cleaned before being put back into use.”
Virgin Trains East Coast operates the service from London to Edinburgh. Places served by the route include Berwick, Newcastle, Darlington, York, Leeds, Lincoln, Doncaster and Peterborough.
Source: BBC Yorkshire