Opposition parties last night raised doubts about the £6.2 billion project to upgrade IT in the NHS after a key contractor pulled out.
Accenture has handed over its responsibilities for delivering the programme in the north-east and east of England to Computer Science Corp (CSC), in a nine-year contract worth about £1.9 billion.
The upgrade will see all patient records transferred from paper to computers, and will introduce an electronic appointment booking system and e-prescriptions.
But the scheme has been dogged by delays and the National Audit Office (NAO) earlier this year criticised the department running the project, NHS Connecting for Health, for failing to properly consult staff.
Last night shadow health minister Stephen O'Brien called for a full review of the project, saying: "If Accenture are willing to cut their losses that seriously undermines confidence in the whole programme.
"The government's failure to ensure that its Connecting for Health programme consulted widely enough and fully engaged users in the design and implementation has led to serious disillusionment amongst frontline NHS professionals.
"By failing to deliver quickly, the cost of the lost opportunity to improve patient care is rising dramatically."
He raised questions about CSC's ability to cope with the extra work - it is already leading the project in the north-west and west Midlands - and said the heat was now on iSoft, the firm Accenture said was not delivering the software fast enough.
"The NHS IT programme was conceived in haste by a prime minister in need of a headline. Accenture's exit is a mark of the questionable procurement undertaken by the Department of Health," Mr O'Brien added.
"In the name of saving money it encouraged providers to bid far lower than they could afford. It is time the NAO conducted a full zero based review of the programme, as the Conservatives promised at the last election."
Liberal Democrat health spokesman Steve Webb said the news about Accenture was evidence of a project "in deep trouble".
"This firm's departure will generate yet more fears that the NHS IT project's costs and problems will escalate further," he said.
"Inevitably, when you change supplier there will be handover costs and the danger that people with valuable knowledge will leave."
However, last night health minister Lord Warner stressed: "We cannot expect a ten-year programme on this scale... a massive civilian project, to actually never have any hiccups along the way."
He told BBC Radio Four's World Tonight: "I don't believe this will mean any significant delay. CSC have got a good track record... I would expect there to be a smooth transfer of responsibilities."