Power supplies to rail routes in the South East are to be improved with a �1bn investment.

The funding boost, announced by the Strategic Rail Authority on Thursday, should allow new trains to replace decades-old rolling stock more quickly.

It comes as other planned upgrades in the region and across the UK are delayed or downgraded.

The problems with power supply have hampered the introduction of new rolling stock on Connex services, with new trains left waiting in sidings to be introduced one by one.

People will have a smooth ride on lovely comfortable trains Wendy Toms, Rail Passengers' Committee for Southern England

The plans to improve the power system should mean more of those trains can be brought into use and the remaining slam-door trains - among the oldest in the country - phased out.

The move was welcomed by Wendy Toms of the Rail Passengers' Committee for Southern England.

"Instead of getting onto tatty, draughty, cold, uncomfortable rolling stock, over 40 years old, which is noisy and rattles, people will have a smooth ride on lovely comfortable trains," she said.

Sheer madness

But the SRA has ruled out electrifying the diesel line from Ashford to Hastings.

Norman Baker, MP for Lewes in Sussex, was critical of the decision not to electrify the line - Sussex's main link to the Channel Tunnel terminal at Kent's Ashford International station.

"Not to electrify that is sheer madness," he said.

"It''s a small gap in the network and business people in my constituency want to get to the Channel Tunnel properly by rail, not having to chop and change onto 1950s diesels at Hastings to get to Ashford."