Birmingham Grand Central is being promoted by some experts

The current station lacks space for both passengers and trains but the redevelopment only provides extra capacity for people.

Now other projects are being promoted such as building underground or a new station in the Eastside of Birmingham.

Network Rail says the Birmingham Gateway project is the best solution and is good value for money.

Stuart Davies, a rail consultant, said: "Birmingham New Street - in terms of the number of trains handled - is working at maximum capacity.

"It's all well and good having a showpiece railway station but you've got to have the level of trains to match it below surface."

'World class city'

One plan favoured by some is to go underground such as in Zurich where a new tunnel and platforms have been built underneath the main station.

But recent studies show tunnelling beneath Birmingham city centre will cost more than �1bn so a plan to build a completely new station - Grand Central Station - is also being touted.

Colin Stewart, from ARUP Consultancy, said: "New Street is limited because of the tunnel approaches so the big benefit here is that we can bring trains in from all different directions around Birmingham into the centre."

Plans to provide extra train capacity have been drawn up according to Network Rail but not as part of the current project.

Peter Strachan, route director, said: "We believe we've got the right solution, it is good value for money and it will give Birmingham precisely what it needs - a new station for a world-class city."