ISoft's problems have delayed its annual results for several weeks

Isoft said the problems mainly related to stating revenues earlier than they should have been.

An independent probe into its accounting problems also concluded there were grounds for a more formal investigation, iSoft added.

Earlier this year, the group was blamed for delays to a �2bn upgrade of the NHS computer system.

Among other problems has been a delay to the publication of its annual results and the departure of its chief executive.

'Irregularities'

"The conclusion of the initial investigation is that there is evidence of irregularities affecting the financial years ended 30 April 2004 and 2005," the group said in a statement.

ISoft announced it had suspended Steve Graham, who held the post of commercial director at the time of the problems, until a more formal investigation has been carried out.

One other employee has also been put on a special leave of absence, while others that appeared to be involved in the problems have since left the company, it added.

Shares in the group have nosedived since news of the NHS problems in March, when they stood around the 165 pence level.

Following news of the results of its latest investigation, shares in iSoft had fallen 2.75p, or 4.62%, to 56.75p in early trade on Tuesday.

ISoft was forced to delay its annual results twice in July - once because of a change in accounting rules and again after it uncovered accounting problems.