Train passengers face greater congestion on the rail line linking Norfolk and Suffolk with London as new figures suggest a dramatic increase in rush hour commuters over the next 30 years.

Network Rail has predicted peak traveller numbers could grow by up to 75% by 2043, heightening calls for radical infrastructure improvements to increase capacity on the line.

Norwich MP Chloe Smith, who is leading a campaign for rail improvements, said the report underlined why serious rail improvements were needed.

She said: 'What this shows is that our line is very popular. Many thousands of people who currently travel from Norwich and the area into London, already know that we need faster journey times, more reliable journey times and a better quality of carriage. 'These things will obviously serve existing and future passengers. But we also want to encourage businesses to set up in our region because they know the transport infrastructure can support them.

She added: 'Anyone who has been in standing room only as I have been many times on the 6pm from London to Norwich knows it is a busy line. This report gives us the proof that we need to keep making the case for the improvements that we need.'

MPs and business leaders have set out a blueprint of improvements they woud like to see including crucial track upgrades, faster trains, new stations and more frequent services.

The Network Rail data suggests peak passengers numbers along the Great Eastern Mainline could grow from 19,500 in 2011 to up to 34,100 a day by 2043.

The figures take into account economic and population predictions and plans by local authorities to build housing.

Network Rail said the figures would be used to inform investment decisions on the capability of the rail network and the train services which operate on it.

It said: 'The ramifications of these decisions are profound, as railway assets such as signalling systems and rolling stock are both expensive and long-lasting. A long term vision is therefore required to optimise the value of future investment and to avoid procurement of redundant assets.'

Guy Dangerfield, from passenger watchdog Passenger Focus said: 'It appears that demand will grow strongly in the coming years and passengers will need to know where the extra seats will come from to stop crowding simply getting worse'.

Chris Starkie, managing director of local enterprise partnership New Anglia, also said the figures showed the case for investment.

He said: 'You will find of all the routes into London, the Norwich to London line is the one that poses the biggest capacity problem for Network Rail. It is the particular route they have the least solutions for. Other routes are overcrowded aswell, but they have plans in place.

'The route into Liverpool Street is the biggest headache. For us it underlines the case for investment, and we believe that with investment that growth in passengers will be even bigger than that forecast.'

Paul Plummer, group strategy director at Network Rail, said: 'Rail plays a critical role in the economy of London and its surrounding area and will face continuing challenges to deal with the growing demand, driven in part by the projected substantial increase in Greater London's population.'

The wide ranging report into rail services across the south eastern region said demand for rail services in the London and South East region was determined principally by the level of employment in central and inner London.

It said greater London was characterised by the highest housing costs in London and the South East but also the greatest range of employment opportunities, and as a result, higher rates of commuting growth into central London were expected from areas of the South East outside Greater London.

A Greater Anglia spokesperson said the study was 'an important building block' in determining the additional future investment and upgrades needed for railways in the region.

She said: 'Despite our short franchise, we have already been playing a major role in securing regional rail improvements - by playing a pivotal part in the development of the East Anglian Rail Prospectus and working with stakeholders to make the case for upgrades over the rest of this decade. Already significant progress is being made with commitments to upgrades at Bow junction near London and at Ely. We are also consulting with regional MPs, local councils, business organisations and user groups about priorities for improvement during the Greater Anglia extension period and working with key regional stakeholders (including Network Rail) to try and achieve further infrastructure enhancements as soon as possible.'

She added the Network Rail initiative again demonstrated the strong case for investment in the rail network.

'We are passionate about building on the improvements we've already made to punctuality, customer service and timetables (such as the hourly Ipswich to Lowestoft service), by working with stakeholders to secure the investment and upgrades necessary to deliver an even better rail service for the region.'