IT firm Accenture has pulled out of key parts of a beleaguered £6.2bn upgrade of the NHS computer system.
The government has been urged to reconsider its plans
American firm Computer Sciences Corporation has taken over Accenture's £1.9bn contract to implement the Connecting for Health programme.
Accenture had responsibility for the roll-out in the North East and East of England but is making big losses on the work and faced fines for late delivery.
Problems at another contractor, iSoft, have delayed the project.
Accenture will keep responsibility for other parts of the NHS programme, including providing a system that will allow X-rays, scans and other images to be available at the touch of a button.
But there are now concerns that its departure could mean further delays at Connecting for Health - which aims to link more than 30,000 GPs with nearly 300 hospitals by 2014.
The government was last week urged to reconsider the plan.