The High Speed 2 rail project could be scaled back in northern England to cut costs.
Under plans drawn up by the panel reviewing the project, the route beyond the East Midlands to Leeds and Sheffield would be axed.
Train speeds would also be cut by 40mph, in a bid to save more than £10bn, according to the Financial Times.
The panel, which is lead by former HS2 chairman Douglas Oakervee, is also looking at ditching the track development into Euston station and instead ending the line in a new hub in west London.
There is a lot of pressure to find savings for the project which has seen projected costs soar by £20bn to £88bn.
The completion date has also been delayed to between 2035 and 2040 from 2033.
Cutting railway speeds from 250mph to 210mph would mean the line is as fast as Japan’s bullet train but would save around £8bn due to the cheaper components used.
The current plans would see a Y-shaped line built, with the first phase going from London to Birmingham where it would split, and then one leg going to Manchester and the other to Leeds, with a new East Midlands hub between Nottingham and Derby. There would also be a branch through Sheffield.
Any proposals to stop the construction of HS2’s eastern leg will be resisted, with the possibility already being criticised.
Permanent secretary at the Department for Transport, Bernadette Kelly, told MPs this week that the northern part of the railway was more likely to be scaled back because it is yet to get parliamentary approval.
There is “more scope” for changes to the northern lines than the first phase from London to Birmingham, she said.
The leader of Leeds city council, Judith Baker, said failure to deliver the line into Leeds and other parts of the north as promised would “condemn the north and east of the UK to second-class status”.
“There will be grave long-term consequences for the economy of the north and east of the UK if the eastern leg of HS2 isn’t delivered in full,” she said.
“It would sacrifice the £600m of annual GDP growth forecast from better connections between Leeds and Birmingham alone, while also putting at risk the expected 50,000 additional jobs HS2 would create in the Leeds city region.”
A spokesperson for Transport for the North said: “As indicated in the HS2 Phase 2b command paper, there is spare capacity on both the Western and Eastern legs of HS2 that could be used to deliver wider regional connectivity. It would therefore be a huge missed opportunity if the current ambition for HS2 and the benefits it could deliver for the North East of England are scaled back.
“In Transport for the North’s submission to the Oakervee Review we have asked that in any review of governance structures of HS2 that TfN is included on the HS2 Board so that the North has a direct say over future development and construction of the northern legs.”
The panel is expected to provide a report on its findings later this month but the government will have the final say on any recommendations made.
The Department for Transport said: “We are not going to pre-empt or prejudice this work with a running commentary on the review’s progress.”