An MP has demanded that Ministers reveal the full route of a £33 billion high speed rail line, after Department for Transport documents showed plans for services north of Birmingham had been quietly downgraded.

Richard Burden (Lab Northfield) said: “We are being asked to make decisions about high speed rail without being given the full facts.”

In the most dramatic change, services to Liverpool will be slower than originally planned – casting doubt on whether the existing cross-party consensus in favour of the planned high speed rail line, known as HS2, can be maintained.

Labour’s Shadow Transport Secretary Maria Eagle – a Merseyside MP – has condemned the “sneaky move”, which has seen plans for a high speed rail link to the outskirts of Liverpool quietly dumped. Instead, commuters to Liverpool will enjoy a high speed service only as far as Lichfield, in Staffordshire, before trains switch to conventional track for the rest of the journey.

And a new proposed timetable shows that other services have also been quietly downgraded.

Proposed services to Warrington, in Cheshire; Wigan, Greater Manchester; Darlington, County Durham, and York, have all been reduced.

The cuts affect destinations which are not on the high speed line itself but are due to benefit from hybrid services, which make use of the high speed line before switching to conventional track to complete the journey.

While attention has tended to focus on the prospect of faster journey times between Birmingham and London, with trains running from a new Curzon Street station in Birmingham to London Euston, the economic case for HS2 hinges on plans to create a nationwide network which transforms connections between Midlands and the north as well as London.

A proposed timetable was included in a document published by the Department for Transport in February 2011 called Economic Case for HS2: The Y Network and London West Midlands.

But a revised timetable, showing a reduction in services, was released by the Department last month in a document called Economic case for HS2: Updated appraisal of transport user benefits and wider economic benefits.

Officially, no decisions have been made about services on the “Y-shaped” network, which will run north of Birmingham in two directions, towards Manchester in the north west and Leeds in the north east. A formal consultation is due to take place in 2014.

But meanwhile, MPs will be asked in 2013 to vote on a hybrid Bill allowing work to begin on the first part of the project, the line between London and Birmingham.

Mr Burden said: “The point of HS2 is not to reduce journey times between Birmingham and London. It’s really about creating a national rail network with Birmingham at its heart.

“From Birmingham’s point of view, connectivity with the north is critical.

“It’s precisely for this reason that Labour have been saying the Bill should include the whole route, not just the first phase.

“Officially, we don’t know what the final route will look like. But at the same time, the Department for Transport is publishing documents which show it must have a good idea what is planned.”

The latest documents show that trains will no longer stop at Warrington, in Cheshire, which was due to have services once an hour.

Wigan was to have two services per hour to London, but this has been downgraded to one service an hour which will finish at Birmingham.

Darlington was to have three services an hour – one to Birmingham and two to London. It will now have two, one to Birmingham and one to London.

York was also due to have three services an hour, and these have also been cut to two services in the same way.

Some towns and cities will receive better services than expected. Services to Runcorn, in Cheshire, have been upgraded from once an hour to twice per hour.

And Durham, which had not previously been included on the line, will now get one service to Birmingham.

The number of services between Birmingham Curzon Street and London have been cut from four per hour to three.

But services from Curzon Street to Manchester have been increased from two per hour to three.

There will be continue to be five services an hour from Birmingham Interchange – a new station near the NEC – to London, as previously announced. But two additional services have been added from Birmingham Interchange to Heathrow Airport.

Meanwhile, a group of 18 local authorities opposed to a £32.7 billion high speed rail line have threatened the government with a judicial review.

They include Lichfield District Council, Warwick District Council, North Warwickshire Borough Council, Warwickshire County Council, Stratford-on-Avon District Council and Coventry City Council.

A letter from the group to Justine Greening, the Transport Secretary, cites five grounds on which it believes errors were made in reaching a decision it labels “unlawful.”

MPs opposed to HS2 have also vowed to keep up their fight in Parliament, despite the Government’s announcement in January that it will go ahead with the project.

Business and council leaders are firmly behind plans for high speed rail, arguing it will boost the West Midlands economy and create thousands of jobs.