DRIVER shortages are pushing earnings on the privatised railways beyond #50,000 a year in some cases as operators seek to cover shortfalls by ''buying out'' rest days with huge premium payments.

With all operators - with the exception of ScotRail - now paying minimum rates of #20,000 or more a year for a 37-hour week there are also increasing numbers of driver inspectors and even a few managers seeking retraining as drivers to take advantage of the situation.

It is understood that these exceptional figures refer to South West Trains where Perth-based owners Stagecoach last year shed 70 drivers only to be faced with widespread cancellations and only just escaped huge fines. Average earnings at South West Trains are said to be #35,000 although the company refused to discuss earnings .

Aslef, the drivers' union, estimates that the passenger and freight operators are collectively short of between 400 and 450 drivers as a result of cuts, wastage, expanding business and the introduction of a 37-hour week. In addition it is estimated that some 2000 new train drivers will be required over the next decade.

The train operators' immediate reaction to the staff crisis is to throw money at it on the grounds that it is cheaper to pay drivers hefty premium payments than the heavy fines the Rail Regulator would demand if performance targets are not hit.

Their medium term approach to the problem is to seek to poach fully-trained drivers from their competitors while in the longer term the solution is to take on new recruits to be trained up by MIllennium Drivers the 50-50 venture by Aslef and the Virgin Rail Group set up last December and shortly to be formally opened with centres at Polmadie, Glasgow, as well as Crewe and London.

A majority of the 26 or so privatised rail companies have been advertising for ready-made drivers in recent months and there are five advertising in the current issue of the union's Locomotive Journal including Virgin , which is offering earnings of #23,000 or more, and Chiltern Railways which is offering some #24,500. Rest-day working and overtime could boost these figures considerably.

Since Aslef general secretary Lew Adams used the letters column of The Herald last week to warn of possible industrial action by drivers and/or poaching by rival operators unless ScotRail negotiated a restructuring deal offering a basic of #20,000-plus, ScotRail managing director Alastair McPherson has offered to reopen negotiations in April ''so that we can progress these matters to a mutually acceptable conclusion''.

Meanwhile English, Welsh and Scottish Railways is determined to concentrate its Customer Service Delivery operation on Doncaster by October. According to the US-owned company the 300 staff currently located in Glasgow (40), Cardiff, Crewe and Nottingham are being offered ''attrac-tive'' packages to move to Doncaster or take redundancy.

q Aslef is to seek damages and legal moves to clear the name of a train driver who served a prison sentence after pleading guilty to manslaughter over a train crash which killed five people eight years ago.

Aslef said it believed Robert Morgan should be exonerated of blame over the crash at Purley, South London, in 1990, in which five people died and 88 were injured.