The chief executive of the beleaguered UK health IT software company iSoft has resigned, less than a week after the company restated its accounts.

iSoft said that Tim Whiston was resigning with immediate effect, five days after telling analysts he had not considered stepping down.

Whiston said in a statement: "My primary concern is for the future success of iSoft and the welfare of its customers, management and staff. I have become increasingly concerned that my continued role with the company may represent a source of negative speculation and comment, being an unhelpful distraction to those within it."

Whiston, who was previously chief financial officer of iSoft, is thought to be in line for a severance package of approximately £500,000, equating to just over a year’s salary.

The firm’s shares have slumped 86% in the past year.  Problems have included being named by partner Accenture as contributing to delays to the NHS IT programme, now running at least two years late. Delays by iSoft in delivering its next generation Lorenzo clinical software have also had a significant impact on the firm’s revenues.

Chairman John Weston, who will act as chief executive until a replacement is appointed, said the business was "creative and innovative", despite the current problems.

"I believe that the business, despite the current difficulties, is a creative and innovative company that has the opportunity to build on a successful track record in healthcare software and develop its leading position in this market. We have a clear set of challenges ahead, but with the necessary determination, we will get through them," he said.

Last Thursday the company announced that it was to restate its accounts in a move that eliminated £165m of historic revenue previously recognised over the past three years, although the company said this will now instead be seen in future years.

The Manchester-based firm also said it will make 150 of its UK staff redundant by the end of the year: approximately 15% of its UK workforce.

The company, which earlier this month sold its Swiss operations, also says it will also look at disposing of other assets. These are understood to potentially include its services division and other country operations outside the UK.