The Birmingham to Crewe leg of high speed railway HS2 will be delayed by two years to cut costs.
Some of the design teams working on the Euston end of the line are also understood to be affected.
Transport secretary Mark Harper blamed soaring prices and said it was “committed” to the line linking London, the Midlands and North of England.
HS2 has been beset by delays and cost rises. In 2010, it was expected to cost £33bn but is now expected to be £71bn.
“We have seen significant inflationary pressure and increased project costs, and so we will rephase construction by two years, with an aim to deliver high-speed services to Crewe and the North West as soon as possible after accounting for the delay in construction,” said Mr Harper.
Mark Thurston, chief executive of HS2 Ltd, recently told the BBC that he and the government were examining the phasing of the build and the timing.
Mr Harper called the decision “difficult” but said it was part of “controlling inflation and reducing government debt”.
John Foster from business group CBI said the delay will ultimately reduce investor confidence in the rail sector.
“Delays to projects may create short-term savings, but they can ultimately lead to higher overall costs and slow down the UK’s transition to a better, faster and greener transport network,” Mr Foster added.
The project is grappling with the rising cost of materials due to the high rate of inflation.
The government hopes that the delays will allow it to spread the cost over a longer period of time, making it more affordable by reducing annual expenditure.
Chancellor Jeremy Hunt, who will outline his Budget next week, wants debt to fall as a percentage of GDP within five years – a target explicitly set by the Prime Minister.
Conservative MP Simon Clarke, former chief secretary to the Treasury, tweeted that delaying construction “would be a sensible decision”.
“Having observed HS2’s progress as chief secretary, I have serious doubts as to value for money and cost control,” he said.
Michael Fabricant, Conservative MP for Lichfield, Staffordshire which contains part of the HS2 line, said: “I shall be asking the government whether this delay marks the end of HS2 north of Birmingham for good and whether HS2 will make good the damage already done in southern Staffordshire.
He added: “Simply saying the project is delayed is not good enough. The area has been blighted by whole fields turned into construction sites.”
Last week, Mr Thurston said the impact of inflation had been “significant” in the past year, “whether that’s in timber, steel, aggregates for all the concrete we need to use to build the job, labour, all our energy costs, fuel”.
He said HS2 was working with suppliers and the government to find ways of mitigating rising costs.
“We’re looking at the timing of the project, the phasing of the project, we’re looking at where we can use our supply chain to secure a lot of those things that are costing us more through inflation,” he said.
HS2 trains are scheduled to carry the first passengers between Old Oak Common station in West London and Birmingham, between 2029 and 2033.
Euston station in London is currently scheduled to open later, by 2035. Further stretches to Crewe and then to Manchester are due by 2034 and 2041.
Most of the HS2 leg to Leeds was scrapped in 2021.