Management consulting group Accenture has reported a 67% profits drop after accounting for expected losses from building a new NHS computer system.
Accenture admitted underestimating the scale of the problem
Second-quarter net income fell to $69.7m (£40.1m) from $209.8m a year earlier, the US company said.
It partly blamed delays by its UK partner in the NHS project, iSoft, in delivering vital computer programmes.
Accenture now fears that the system will not be used by the NHS as widely as had previously been forecast.
The $3.5bn contract with the NHS was for Accenture to help design, build and manage information systems to support patient care through electronic medical records, appointment booking and prescription systems.
In the light of the delays, the UK government had now decided to let doctors use alternative computer systems, said Accenture Chief Financial Officer Mike McGrath.
Despite telling shareholders in July last year that the company had resolved its problems with the contract, it has now warned that the problems had been underestimated.
"I am taking personal responsibility for getting the NHS issue behind us," said chief executive Bill Green. "These results are unacceptable."
However, Accenture said it would try to renegotiate the terms of the deal in a bid to stem its losses.