RAIL passengers have accused ScotRail of deliberately running a ''ghost train'' on the London to Fort William sleeper, claiming it wants the service withdrawn.

ScotRail yesterday admitted that coaches on the trains occasionally run empty despite passengers being told the service is fully booked, but blamed this on timetable and booking errors. A spokesman described accusations that it was deliberately undermining the service as ''absolute nonsense''.

Two sleeper trains run in each direction between Scotland and London Euston every night except Saturday. Services from Aberdeen, Inverness, and Fort William merge to form the Highlander, while trains from Edinburgh and Glasgow merge to form the Lowlander.

Maureen Macmillan, Labour MSP for the Highlands and Islands, said rail users were regularly refused sleeper tickets and told the train was fully booked, only to discover later that it was in fact half empty.

She was among six concerned rail users from across the UK who wrote a joint letter to The Herald this week to highlight the problem.

Speaking yesterday, Ms Macmillan said: ''It is extremely difficult to get a ticket. Some people ring up and are told there is no such thing as a sleeper from London to Fort William. Others are told it is fully booked when it is not..''

Donald Murdie, a former railwayman who lives on Lewis, also wrote to The Herald. He claimed a member of staff at ScotRail, whom he refused to name, had told him the coaches were deliberately left empty.

The train operator insisted there were no such sinister motives, and said it was ''utter rubbish'' to suggest it would deliberately run empty trains.

A ScotRail spokesman said the letters to The Herald emphasised that service on the train was excellent, which he claimed ''gave the lie'' to claims ScotRail was deliberately trying to undermine it.

The so-called ''deerstalker'' sleeper service was given an eleventh hour reprieve in May 1995 following a ruling by the Court of Session in Edinburgh. This followed a campaign waged by Friends of the West Highland Line and Highland Regional Council against a decision by British Rail to close the service on cost grounds.

In 2002, National Express said that unless more public money was provided for the service, the company could not afford to run it.