iSoft's is trying to reassure investors

Tim Whiston said he feared there would be "negative speculation and comment" if he stayed in the post.

The firm hit the headlines in March after it was blamed for delays in a �2bn plan to upgrade NHS computers.

There has been speculation that the project may be delayed for as long as two years.

Distraction

After iSoft issued a profit warning last Thursday, its shares dropped 32 pence, or 39%, to 51p. They now stand at 57p.

We have a clear set of challenges ahead, but with the necessary determination, we will get through them John Weston iSoft chairman Check iSoft's share price

Mr Whiston said quitting had been a difficult decision, but he was doing so for the good of the company.

"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," he said.

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.

"We have a clear set of challenges ahead, but with the necessary determination, we will get through them," he said.

Reassure investors

The main reason iSoft will miss its profit forecast is that it plans to change the way it reports earnings.

It expects pre-tax profits of between �3m and �7m for its past financial year, compared with an earlier estimate of �17m to �22m.

In an effort to reassure investors after the NHS story emerged, iSoft said it was looking at ways of cutting its costs, including reducing its staffing levels and selling off assets.