'We can't go on like this' - Chancellor George Osborne will be told in a business-backed dossier making the argument for a £476m infrastructure investment in the rail link between Norwich and London.

The business case published today - which will land on a number of top Government desks - sets out the potential £4.5bn payback from allowing passengers to reach London from Norwich in 90 minutes, more reliably, and in newer carriages.

Senior figures will be told that missing the crucial opportunity for investment will 'stifle growth', 'run our service into the ground' and will condemn passengers to 'at least another decade of misery'.

It comes just under a year after Mr Osborne travelled to Norwich to request a taskforce of business leaders, MPs, transport officials and infrastructure firm Network Rail, should set up a taskforce to set out how faster and more reliable train journeys could be achieved.

The taskforce has found that investment of half a billion pounds could transform East Anglia's main rail line – and create tens of thousands of jobs for the region.

It's business case claims that each pound invested in the line will bring almost £10 in economic benefit for the region – four times the cost/benefit figure for the proposed HS2 line from London to the midlands and north of England.

In a letter to the Chancellor, New Anglia chairman Mark Pendlington and Norwich MP Chloe Smith said: 'We could be the California of Europe, yet we have some of the oldest trains in Britain and our passengers pay some of the highest fares to subsidise other lines in the country.

'Our rail service is over-crowded, the infrastructure is not resilient to failures. It is as quick to go 225 miles over land and sea from London to Brussels as it is to travel on the train from London to Norwich, half the distance.'

Next month Mr Osborne will set out his mini-budget, and the co-chairs added: 'The Chancellor's decision for this Autumn Statement is simple: we ask him to confirm the infrastructure improvements needed to unlock the economic potential of the region through faster and more reliable services; and provide for new rolling stock on the Great Eastern Main Line for better journeys.'

The business case claims that proposals will create 8,200 new jobs in Norwich, just under 10,000 new jobs in Ipswich, some 16,000 new jobs in helmsford and 14,000 in Colchester.

Labour's shadow transport secretary Mary Creagh said her party wanted better services on the Great Eastern Main Line, adding: 'David Cameron will be judged on his actions, not words'.

She claimed that Government caused chaos in the franchising programme has led to three short term contracts on the route since 2010, and delayed investment in trains.

Adding: 'A Labour government will cap rail fares, legislate for a public sector operator, devolve the running of regional and local services and deliver a railway which puts passengers first.'

Norwich candidates Jessica Asato said: 'Labour strongly supports improvements to the Great Eastern ‎Main Line and belated investment from the Government would of course be welcome.

'The social and economic case for investment in the East is compelling, but if, as Chloe Smith MP has stated, the money is already there, why hasn't the Government taken the opportunity in the last four years to get the ball rolling? This does nothing to help Norfolk commuters on overcrowded unreliable trains who have been hit by inflation-busting fare increases of 20pc since 2010.'

Clive Lewis, who is standing for Labour in Norwich South, said: 'Alongside the need for greater investment, Labour would address passenger concerns about the cost of fares and the quality of service by introducing a public sector rail operator to take on rail franchises, as well as devolving control of regional rail to local authorities to ensure greater transport integration.'

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