Virgin Trains have lashed out at the infrastructure of the West Coast Main Line, which links the North West of England with London.
The company has criticised the performance of the line and says it continues to be unacceptable.
They claim the problems are having a major impact on Virgin Trains' customers and those of other operators, who have reportedly seen punctuality fall well below expected levels.
A company statement reads: "We are concerned with the lack of focus on immediate improvement, as we and our customers must see short-term progress, especially as the Olympics and Paralympics will be a showcase for the industry.
"The problem has been highlighted recently as improved weather at the end of May ruined performance through heat-related delays with performance on some days being at around 60 per cent punctuality.
"Anything short of this will affect the potential of the West Coast Mainline to continue its success."