The extension of HS2 to Leeds "will probably not now go ahead", Labour former transport secretary Lord Adonis has claimed.
He made the comment after the Government deferred decisions on the design of that section of the high-speed railway until after publication of an Integrated Rail Plan for the North and the Midlands.
Lord Adonis warned that this means ministers are "delaying indefinitely" the building of HS2 between Birmingham and Leeds.
He wrote on Twitter: "The Government is only now going ahead with the Manchester leg of HS2 and is delaying indefinitely the eastern leg to Leeds, Sheffield, Nottingham and Derby.
"By deferring decisions on (the) eastern leg of HS2 while confirming (the) Manchester leg, the Leeds leg will probably not now go ahead. Phase 2b will probably become just Manchester."
Plans for HS2 involve Phase 1 running from London to Birmingham, Phase 2a from Birmingham to Crewe, and Phase 2b from Crewe to Manchester, and from Birmingham to Leeds.
HS2 minister Andrew Stephenson branded the peer's tweets "simply untrue".
He said: "We've always been clear that the eastern leg is being considered under our Integrated Rail Plan, which by the end of the year will outline how we will deliver better, more reliable services across the North and Midlands."
In the Government's response to a consultation on refinements to the design of Phase 2b, Mr Stephenson said it was "prioritising development of the western leg into Manchester" while "considering the best approach" for the eastern leg.
Lord Adonis claimed "the economic and social consequences of today's HS2 decision are profound".
He went on: "Metropolitan growth in England north of London will now concentrate on (the) Birmingham-Manchester corridor.
"The whole eastern side of England, without HS2, is downgraded. A catastrophically big and bad decision."
Alongside the announcement about the eastern leg, HS2 Ltd launched a consultation on proposals to expand Manchester's high-speed rail platforms.
This is aimed at boosting connections between HS2 and Northern Powerhouse Rail (NPR), which is a project to improve services between the region's major cities.
HS2 Ltd is also proposing to enhance its plans for Crewe station to enable it to be served by more HS2 services, and to build a train depot at Annandale, in Dumfries and Galloway.
Tim Wood, a director at Transport for the North, a cross-party group of northern leaders, said it was crucial that investment in HS2 and NPR "allows for benefits to be shared equally across the North".
He went on: "We absolutely want to see the HS2 eastern leg developed.
"It dovetails entirely with our plans for Northern Powerhouse Rail and would deliver unrivalled rail connectivity to communities. That's not only better and faster services to the likes of Leeds and Sheffield, but further beyond to York, the North East and up to Scotland.
"The Oakervee Review outcome recommended committing to the full HS2 plan, helping to level up the economy.
"We hope that the Government's Integrated Rail Plan, set to be published later this year, will commit a sustained pipeline of investments for the North that includes both HS2 and Northern Powerhouse Rail."