A 300MPH “floating train” that would carry passengers from London to Manchester in 55 minutes is to be studied by the Government after winning the support of Tony Blair.

The Prime Minister believes that the magnetic levitation (maglev) line would help to arrest the decline of northern cities by creating fast, frequent connections with the capital.

The £30 billion line, which would use magnetic forces to lift and propel trains on a cushion of air, would be built in stages from London to Glasgow over the next 12 years. It would carry 6,000 passengers an hour on driverless trains at a top speed of 311mph.

The technology has been demonstrated on Shanghai’s 19-mile airport link, which opened in December 2003 and carries passengers into the city in eight minutes, compared with the hour it can take by car.

Gordon Brown, the Chancellor, travelled on the Shanghai line this week and is understood to be keen on investigating its potential.

The Government announced this month that demand for rail travel was growing so rapidly that a high-speed line between London and Scotland could be needed “over the next 10 to 20 years”. Maglev will be one of the options considered. Ultraspeed, the British company promoting the German technology used in Shanghai, made a presentation to Mr Blair at Downing Street last year.

In a letter this week to Jack Cunningham, a Cumbria Labour MP and former Cabinet minister, Mr Blair wrote: “We are ready to look at the potential of maglev alongside more conventional high-speed rail technologies in the work being taken forward.”

The core route would run from Glasgow to Edinburgh, down to Newcastle, across to Leeds, then Manchester and down through the Midlands, before branching at the M25 to stations at Heathrow in West London and Stratford in East London. The line would not be extended to the centre of London or other big cities because of the difficulty of building through densely populated areas. But by the time the line fully opened in 2018, the two outer-London stations would be linked by Crossrail.

Terminating on the outskirts would also enable Ultraspeed to build large carparks, helping it to compete for passengers who prefer to drive to airports and catch domestic flights.

Alan James, the project leader, said that the maglev guideway would occupy far less land than a conventional rail line because it could be built on stilts set 70 yards apart. This would reduce the cost because roads would not be redirected. The maglev could cope with gradients as steep as one in ten, meaning that fewer expensive tunnels would be needed.

Ultraspeed, which has invested £2 million in developing its plans, said that 70 per cent of the cost could be financed by the private sector. That would leave the taxpayer to find about £9 billion.

Mr James said that a 30 to 40-mile section of the route would be built in a £1.8 billion pilot project to demonstrate the benefits and prove that costs could be controlled. One option would be to link Liverpool and Manchester airports. Others are Edinburgh to Glasgow and Tyneside to Teeside.

But Ultraspeed has alienated some officials in the Department for Transport by going straight to Downing Street. One official said that the scheme would present too big a gamble. “Nowhere in the world has a full-length maglev line,” he said.

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