First Great Western has made the shortlist for the route

First Great Western, Wessex Trains and Stagecoach are bidding to run the Greater Western rail franchise.

Christopher Irwin of the Rail Passengers' Committee said the proposals could harm service levels.

"The franchise is driven by a desire to minimise government expenditure, rather than effective delivery of a service," he said.

Mr Irwin added: "There is already widespread concern in the West country and in Wales about the draft timetable.

"Passengers who are aware of the detail are deeply concerned about whether this is the right way of awarding franchises."

We believe we can offer a bid that will offer improved services and better value for money Steve Stewart

Mr Irwin said passengers were worried that the franchise would put "operating convenience before the needs of passengers."

The Greater Western franchise, due to commence in 2006, will merge the current routes of First Great Western, Great Western Link and Wessex Trains.

The franchise area covers the West country to London.

Companies have until 26 September to submit their bids to the government.

The winning bidder will operate long-distance, regional and local services in the Thames Valley, Cotswolds, Bristol and the surrounding area and the West of England with some cross-border services into South Wales.

'Analyse bids'

The Strategic Rail Authority (SRA) is currently being replaced by Department for Transport (DfT) Rail which will pick the final winner next winter.

Chris Atkinson - of DfT Rail told the BBC: "After 26th September we will analyse the bids which takes about three months.

"Then, round about the turn of the new year, we shall announce the new preferred bidder and the new franchise will begin operating on 1st April."

Steve Stewart of Stagecoach said: "We are expecting tough competition to run the franchise but we have a first-class team that has excellent experience for the challenges involved.

This is a very big and diverse franchise Richard Gibson

"We believe we can offer a bid that will offer improved services and better value for money as well as providing the right return for shareholders, so we are certainly on track with our bid."

First Great Western currently operates about 84% of the rolling stock on the three franchises which are to be merged into one in 2006.

Tim Bowcock of the Swindon-based operator said: "We are currently consulting with stakeholders and passenger groups.

"We will then filter those into the bidding process which will go to the Strategic Rail Authority."

National Express, the coach carrier and parent company of Wessex Trains, is the third bidder hoping to run the new franchise.

Richard Gibson of the company said: "This is a very big and diverse franchise.

"We are confident that we have the experience to deliver a good service to customers and shareholders as well as encouraging more people to use the railways."