Power supply problems could result in £1 billion worth of new trains not being able to run at their full capability on a busy commuter line for two years, it was revealed today.

The first of the Desiro 450 trains was shown off today in Germany.

But Keith Cochrane, chief executive of South West Trains' parent company Stagecoach Group, said: "These trains won't be able to use their full capability until the power supply is upgraded in southern England."

The upgrading work is being taken on under the auspices of the Strategic Rail Authority and could be completed within a year or two.

When the work is completed, the trains will be able to reach a top speed of 95mph faster and better braking will mean they can stay at their top speed for longer.

The new trains are replacing old slam-door trains on SWT, which runs services from London's Waterloo station to the South Coast and 11 daily services between Brighton and Chichester.

SWT is receiving almost 200 trains from German company Siemens over the next two years.

It showed the first of the trains off at at Wildenrath, northern Germany, today.

l THE rail industry and the Government are being challenged to back a plan for quick improvements to railways in the South-East.

Friends of the Earth today issued the challenge.

The organisation believes the plan could be implemented quickly and at relatively low cost.

It wants the cost of rail travel cut with the introduction of a national off-peak discount railcard and more services to be run when people want them, such as 'night out' trains.

It wants rail bottlenecks at certain junctions dealt with through improved signalling, the rail network expanded with the building of new stations, better transport links provided to stations with secure and well-lit cycle parking facilities and improved information for passengers and improved safety at stations.

It is asking rail passengers to back its campaign by sending an email via its web site at www.stoptrainrobbery.com