Downscaling HS2 would create “a commercial and operational mess”, industry experts have warned.
Prime Minister Rishi Sunak and Chancellor Jeremy Hunt are reported to be meeting to discuss the future of the high-speed rail project in the coming days.
There is speculation the leg from Birmingham to Manchester will be cancelled or delayed while Euston will be axed, both in response to soaring costs.
William Barter, a railway consultant whose recent clients include the Department for Transport, told the PA news agency this would result in “80% of the costs and 20% of the benefits”, while rail engineer and writer Gareth Dennis claimed it would be a “stupid decision”.
Under existing plans, HS2 trains will run on high-speed lines between London and Manchester, as well as running on existing lines to destinations such as Glasgow, Liverpool and North Wales.
Stopping HS2 at Birmingham and not extending the line to Euston means the trains may only be able to be used for a shuttle service between Old Oak Common, west London and Birmingham Curzon Street.
If the planned Handsacre Link goes ahead near Lichfield, Staffordshire, HS2 trains will be able to connect to the existing West Coast Main Line (WCML).
But only the number HS2 trains could run on the WCML is limited to an estimated three per hour as the route south of Manchester has little spare capacity.
It is already used by six passenger train operators and a number of freight companies.
Mr Barter said: “The number of trains you can run is limited by the capacity of Old Oak Common station as a terminus, and the commercial attractiveness of Old Oak Common as a terminus, which is broadly going to be very good for half the people and very bad for the other half.
“That means you probably end up running a West Coast Main Line intercity service that is split between Old Oak Common via the new line and Euston via the old line.
“That’s a commercial and operational mess.”
Mr Barter said in that scenario, the core HS2 route would be “working at about one-third of its operational potential” despite building “the most expensive bit”, which is between London and Birmingham, due to extensive tunnelling, new stations and complex junctions.
He added: “Until you get the railway to Euston, there’s not much benefit in it for anybody anywhere.
“In effect you’d get 80% of the costs and 20% of the benefits.”
Old Oak Common has an estimated capacity of six trains per hour, compared with 17 per hour at Euston.
Mr Barter said: “Without Euston, the last train you want to put into Old Oak Common is an Anglo-Scottish one because they’re carrying people who’ve got luggage and they’re most likely to want taxis to their destination.
“If you chuck them out at Old Oak Common instead of Euston, that’s an additional £30 taxi fare.
“Either that or they’ll be struggling onto the Elizabeth line and interchanging with all their luggage.”
He added: “To get any meaningful use out of anything north of Birmingham, the railway needs to go to Euston.”
Mr Dennis said the “main benefit” of HS2 is creating more space on existing mainlines, enabling more suburban trains to run.
He said: “If you aren’t running the trains to central London then people are going to want the mainline trains to still run on the existing network, which completely destroys the point.
“If you get rid of Euston you massively erode the released capacity benefits, not to mention that the journey time benefits are down by the fact that you have people getting off at Old Oak Common.
“It’s a transparently stupid decision. Only someone doing this for internal party political reasons would be proposing such a thing.”
Mr Dennis said the most significant consequence of failing to build HS2 north of Birmingham would be not getting more services to locations such as Stockport in Greater Manchester or North Wales.
He added: “If you get rid of the line north of Birmingham, you get rid of all those main benefits.”
Mr Barter noted that infrastructure involving the planned HS2 line to Manchester is “shared” with Northern Powerhouse Rail, which is a scheme to boost east-west rail journeys across the North.
He said: “If HS2 doesn’t provide it, Northern Powerhouse Rail will have to all on its own, and that would probably make it unviable.
“You get the best out of infrastructure by sharing it.”
Mr Dennis said: “We always hear the stories of misery of people trying to commute across the North.
“You get rid of HS2, there is no new line across the Pennines.
“Northern Powerhouse Rail doesn’t exist without HS2 going up to Manchester.
“That means all those promises about new northern infrastructure completely evaporate.”