Top-rated publicly run East Coast is to get new high-speed trains in a government-backed deal that will create 730 jobs.

Rail union RMT welcomed the £2.7 billion state investment but warned that it risked being yet another taxpayer giveaway rail "rip-off merchants" if the franchise is handed back to profiteers.

Nearly 500 carriages will be built at Hitachi Rail Europe's factory in Newton Aycliffe, Co Durham, said Transport Secretary Patrick McLoughlin.

The Class 800 trains will start running on the East Coast line in 2018.

The new trains will provide a fifth more seats, reduce journey times between London, Leeds, Newcastle and Edinburgh by up to 15 minutes and improve reliability.

RMT acting general secretary Mick Cash said it was a boost to Britain's only publicly run railway.

He said: "The publicly run East Coast Main Line, using some of the most ageing units on the tracks, is delivering the best and most cost-effective services anywhere on the network, hammering home the case for public ownership of our railways."

But he warned that the investment could be another bung to cowboy companies desperate to get their hands on the line.

"It would be a major scandal if the beneficiaries from the long-delayed East Coast fleet upgrade were another bunch of spivs and rip-off merchants from the private sector," he said.

The contract to deliver the carriages has been agreed with Agility Trains, a consortium of Hitachi Rail Europe and John Laing.

As well as the new Newton Aycliffe factory, Hitachi is also building 369 carriages for the Great Western line and six new maintenance depots.

Hitachi recently announced plans to move its global rail headquarters to Britain.

But Mr Cash revealed the new intercity trains were being built in Japan and "shipped flat-packed to the north-east, where they will be bolted back together.

"Any new jobs are welcome but if the trains had been wholly constructed in the UK we would have been looking at many thousands of skilled engineering posts right across the supply chain."