A FRESH row over rail fares flared today when a leading train company was accused of ''mugging'' passengers by starting to charge for reserving some seats.

The Transport Salaried Staffs Association said the move by National Express was ''outrageous'' and warned that it could spark abuse against booking office staff.

The company is planing to introduce a charge of £2.50 for reserving a single or £5 for a return ticket from this weekend on its East Coast and East Anglia franchises, the union revealed.

TSSA said it was the highest seat booking charge ever imposed by a private rail company and comes at a time when the East Coast franchise holder is reportedly trying to renegotiate its contract with the Government.

Booking clerks have told the union they are so worried about the reaction from passengers that they have warned management they expect regular abuse when they ask for the extra cash.

''All staff will face regular abuse, especially when passengers are spending £223 for an open ticket and then have to pay £5 on top or when a family of four want to reserve four seats and told they will pay an extra £20,'' warns an internal memo from members in York.

Gerry Doherty, the union's general secretary said: ''This is an outrageous imposition on millions of passengers and amounts to the fourth increase in overall prices in just five months.

''What National Express is now saying to passengers is that, if you want to be sure of sitting down on their trains for a return journey, then you will have to pay an extra £5 for a return journey or £2.50 for a single.

''That is simply mugging passengers for an extra fiver, and it will hit the elderly and families the hardest. They cannot risk being forced to stand on long journeys from Newcastle to London and therefore they will be forced to pay the extra.

''If we had a shred of confidence in Geoff Hoon, we would ask him to intervene. But as he is the worst Transport Secretary we have ever had to deal with, we are not hopeful.''

The union has been pressing the Government to halt increases in fares and to stop the cost of Railcards from rising later this month.

National Express confirmed that, from this Sunday, a £2.50 booking fee will apply to some seat reservations on its East Coast and East Anglia routes.

A statement said: ''Seat reservations made on some standard class ticket types are optional for the customer and could apply to about 25 per cent of people travelling.

"If a customer does not want to reserve a seat, there is no charge.

''This does not apply to any advance purchase tickets, first class tickets, season tickets, customers with a disabled railcard or assisted passengers.

''We want to improve the on-board environment for our customers. We do find that people are often reserving multiple seats as they're not sure which train they are going to catch.

''Whilst we understand this, by asking people to pay for a seat reservation, seats will no longer be left empty with a reserved sign, therefore being made available for other customers to use.''

Bob Crow, general secretary of the Rail Maritime and Transport union, said: ''This is another example of National Express bleeding passengers dry in the drive to prop up their profits.

''The sooner the railways are free from this privatised daylight robbery the better and that's why we are stepping up RMT's campaign for renationalisation.''

Liberal Democrat Transport spokesman Norman Baker said: ''Train passengers are having to pay to be taken for a ride by National Express. This is a crude attempt to increase income and is totally unjustifiable.

''Passengers in Britain already pay the most expensive rail fares in Europe. Sitting down on a long and expensive rail journey shouldn't be considered a luxury.''