A funding package to improve the South East's railway infrastructure has been attacked as a "huge missed opportunity" by a business group.

The Government's White Paper, Delivering A Sustainable Railway, is too short-sighted, according to the South East England Regional Assembly (Seera).

The quango called for longer-term funding commitments to allow train operators to plan on the same 20-year timescale as the assembly.

Seera's planning committee said the proposed investment would not keep pace with the region's 20-year growth plan.

The White Paper's funding only extends to 2014.

Committee chairman Councillor Moira Gibson said: "Our South East Plan sets out how we will cope with significant growth by 2026.

"Infrastructure improvements are key but the rail White Paper covers less than half the South East Plan period and offers only incremental change that will not solve current overcrowding, let alone cope with increasing demand.

"The Government's rail paper represents a huge missed opportunity to plan seriously for the future and provide a rail service that will support growing communities and reduce road congestion by providing an attractive alternative to car commuting.

Our evidence base and plans - and those of other regions - are all in the public domain but the Government has failed to align its own thinking and investment with the regions' priorities."

Overcrowding on the Brighton to London line has already forced changes to the Gatwick Express.

From December next year the service will be extended to Brighton at peak times.

Commuters used to being squeezed into carriages like cattle should benefit from a £5.5 billion upgrade of the Thameslink line, announced in July.

But Sussex Enterprise boss Mark Froud said, despite the improvements, the Government's investment in railways was inadequate.

He said: "It is disappointing that the Government hasn't shown more ambition with its plans for long-term investment in the country's rail structure.

In Sussex we know only too well the impact that overcrowding on trains and rail congestion has on our working lives.

"To see a significant improvement to rail services the Government needs to be thinking on a much larger scale.

"However, the White Paper does indicate how far we have come in the past few years. Until recently the rail network was a shambles trying to cope with numerous problems. At least now the Government is starting to look ahead and plan for the future."