Staff from Network Rail claimed flights from Cardiff to Anglesey on expenses as it was cheaper than travelling there by train.

There were a number of occasions in the previous two financial years where staff from the rail organisation travelled by air rather than rail as it was "more cost effective".

A report by the Sunday Times revealed that employees spent £19.99 for a flight from Cardiff Airport to Anglesey Airport. The current rate for rail fares between Cardiff and Holyhead is £84 for a flexible single rail ticket and £32.50 for the cheapest advanced rail ticket.

Network Rail's expenses policy states that UK air travel should be used when it "represents the most cost effective option compared to the relevant train fare" when taking into account the cost of the journey.

Other journeys by Network Rail staff undertaken by plane included a £30.99 flight from London Standsted to Glasgow, a ticket from Exeter to Manchester for £61.99, a ticket from Newcastle to London Heathrow for £73.31, a flight between Birmingham and Glasgow for £47.99 and a ticket from Southampton to Manchester for £39.99.

A total of £1m was spent on rail tickets in the last two financial years while staff took 9,212 flights in the same period.

Plaid Cymru, who have campaigned for better rail infrastructure in Wales, said the situation was "beyond parody".

Jonathan Edwards MP, Plaid Cymru's transport spokesman said: "Wales’s creaking rail infrastructure and broken transport system is clearly not fit for purpose. You can’t travel between the north and south of our country without going in to the one next door.

"The fact that even Network Rail workers find it inefficient to use the railways is beyond parody.

"The Tories in Westminster and Labour in Cardiff Bay have consistently underinvested in vital elements of our transport system. What we need is a mass programme of investment in green transport, so we can have a futureproofed, cost-effective way of getting around Wales."

A spokesperson for Network Rail said: "With 98% of our business travel made by rail, trains more often than not represent best value."