Accenture is to take a £265m charge for losses associated with its contracts to provide new IT systems to the National Health Service.
The outsourcer has also said it wants to renegotiate parts of its contract with the NHS.
The effect of the charge meant that Accenture, which has a 10-year £2bn contract with the NHS, saw its quarterly net profits dive 67%, and led to an initial 8% drop in share prices.
The contract covers the design, building and management of systems that support patient care, such as electronic medical records, appointment booking and prescription systems.
The NHS has closely written contracts with a number of suppliers, which has led to 'fines' being levied for suppliers that have not met technology roll-out goals.
BT, another supplier under the NHS’s National Programme for IT, has already paid fines in the past for the late delivery of technology.
Accenture chief executive officer Bill Green said, "I am taking personal responsibility for getting the NHS issue behind us."
He told analysts, “These results are unacceptable".
Last year Green told investors that problems associated with the NHS contract had been resolved. On reporting the latest results, Green said the company had underestimated the problems.
Green said, “We fully subscribe to the NHS vision of an integrated patient care record. We have established guiding principles for success for our ongoing work with the NHS and have devoted additional management resources at the highest level to resolve the NHS matter as quickly as possible.”
The rest of the business “remained very strong,” said Green.