There are calls for the railway line to King's Lynn to be dualled as proposed timetable changes will leave passengers facing longer journey times.

West Norfolk council, the Fen Line Users Association and King's Lynn Business Improvement District claim passengers will receive a worse service, as longer stops in stations add 12 to 14 minutes to the journey between King's Lynn and London King's Cross.

They say the single line bottleneck imposes 'severe limits on the scheduling of trains', leading to the longer overall journey times now being proposed.

They want the second track between Lynn and Littleport, which was removed to save costs in the 1980s, to be restored to accommodate 12-car trains.

Council leader Brian Long said: 'We've heard much about the promised work on Ely North Junction that is to take place, but that will inevitably be a long process. We also want the single-line sections between there and King's Lynn returned to a two-track line. The single-track bottlenecks result in a sub-standard level of service, which Great Northern is now proposing to downgrade further, with even longer journey times.'

Train operator Great Northern has put its proposed timetable changes out to consultation.

Colin Sampson, chairman of the Fen Line Users Association, said: 'We've said before that more and more people are travelling to Cambridge and London and that they expect a decent train service. The growth isn't a flash in the pan – just look at the official statistics, which show strong passenger growth year after year. Not delivering the promised 'half-hourly' frequency is bad enough, but now they're thinking of slowing things down on top of that.'

Darren Taylor, chairman of King's Lynn BIDd, added: 'King's Lynn businesses are getting increasingly fed-up with false promises and a lack of action from Great Northern. I welcome the bigger trains, but not the long delays before they are to be introduced, maybe over a year away, but we need them twice an hour, all day. I'm concerned that the Fen Line, and King's Lynn specifically, is yet again being overlooked in favour of investment that will benefit other towns and cities in the east. We need to make our dissatisfaction clear to Government.'