National Express East Anglia was last night accused of neglecting its most valued customers after commuters were advised to avoid peak-time evening trains between London and Norwich.

National Express East Anglia was last night accused of neglecting its most valued customers after commuters were advised to avoid peak-time evening trains between London and Norwich.

Fresh calls were made for extra carriages on the mainline route after it emerged it was full to capacity on two of its services from the capital.

'Fully booked' posters went up at London Liverpool Street station on Wednesday asking passengers to avoid the 5pm and 5.30pm trains to Norwich timetabled for yesterday and today.

Officials from National Express East Anglia yesterday said they published the warnings after selling all of their advanced tickets and expecting an increase in travellers ahead of the bank holiday weekend.

But a Norfolk MP last night slammed the company for mistreating its season ticket holders who spend an 'absolute fortune' to not be guaranteed a seat on their daily commute to and from London.

Richard Bacon, MP for South Norfolk, said the rail firm was in the habit of 'annoying' the people of Norfolk and the mainline service needed more trains and rolling stock.

'Season ticket holders pay the price of a small car each year to train companies. They are their most important customers, but they are treated like cattle fodder to get money out of. They should get a seat and should be considered the most special and given preferential treatment,' he said.

Mr Bacon said he would not be surprised if passengers failed to support the rail firm when the Greater Anglia franchise comes up for renewal in 2014.

'We are not at peak season yet and we have already had a lot of problems. What is going to happen in the height of summer?

'It is a serious concern because people are hoping for a good summer for British tourism,' he said.

Season ticket rail passengers pay more than �6,000 a year to travel daily between Norwich and London, but were advised to avoid the 5pm and 5.30pm services because of an increased allocation of advance ticket sales.

A spokesman for National Express East Anglia said it was running an extra service from London Liverpool Street to Ipswich at 5.28pm yesterday and today to ease the pressure.

'We wanted to be up front with passengers that it is busier than normal, but some people have interpreted that they cannot get on the train. We are not stopping season ticket holders from getting on the train of their choice. Raising them as fully booked was misleading and we are rectifying that,' he said.

National Express said there had been no overcrowding on last night's 5pm and 5.30pm trains.

The increased demand on the London-Norwich service comes after the government announced earlier this year that it was investing in 188 new and refurbished rail carriages for National Express East Anglia, which would benefit the west of the region, but would not be used in Norfolk or north Suffolk.

Peter Lawrence, from Norwich, who is also president of Rail Future, a national rail passenger campaign-ing group, said it was common for commuters to stand from London to Ipswich during peak services.

'It shows the popularity of services from London to Norwich and we are seeing more people using rail.

'In the short term, the problem could arise again, but hopefully Network Rail, the train operators and Department for Transport will recognise the need, investigate it, and do something about it,' he said.

Guy Dangerfield, Passenger Focus manager, added: 'This highlights the underlying need for more capacity out of Liverpool Street on National Express East Anglia services in the evenings.'