Now the company's Irish operation is without a boss after the surprise announcement last week that the managing director of the company's operations in Ireland and Scotland will retire.

Advertising executive Seán McCrave left NI last August and was subsequently appointed chief executive of the Institute of Advertising Practitioners in Ireland (IAPI), the advertising industry's representative body.

Last month, lawyers for NI secured a High Court order restraining McCrave, another former ad executive, David Dwyer, and others from destroying records of advertising placements for the Irish Sun and News of the World.

In applying for the order, the company claims that there was a sharp fall in revenues from some frequent advertisers including mobile services company Opera Telecom after McCrave's departure and launched an inquiry. According to the company's lawyers, the inquiry examined the placement of advertising in the Irish editions of the Sun and the News of the World.

The company claimed that DM Media Services and Tower Hatch Ltd, two companies connected to McCrave, were collecting debts related to advertisements placed with the newspapers.

Colin McClatchie, who was managing director for Ireland and Scotland, last week announced his departure, according to a statement from NI, to spend more time working as a non-executive director of Scotland's version of the IDA and as vice chairman of Scottish Opera. The announcement took Scottish observers, who noted that the previous Friday McClatchie had entertained high-level politicians including first minister Jack McConnell at a party at his home, by surprise.

An NI spokeswoman hotly denied Scottish media reports of a connection between the investigation into McCrave and the departure of McClatchie.

"Colin McClatchie and NI agreed he would retire from his position as managing director, Scotland and Ireland before NI had any knowledge of any alleged irregularities in the business dealings of our Irish business and his departure is entirely unconnected with those alleged irregularities."

The spokeswoman confirmed that Ken Hutton remains as commercial director for Ireland but it is widely believed among advertising sources that his departure is imminent. The spokeswoman declined to comment further.

A second statement from NI on Friday announced the appointment of Steven Walker of the Scotsman as general manager for NI in Scotland.

It is understood that NI is currently seeking to recruit a manager for its Irish operations.

McCrave remains chief executive of IAPI. Outgoing IAPI president Jeremy Crisp, who is leaving Ireland to head an advertising agency in the US, sent an email to the advertising community following media reports of the High Court injunction.

"As you might have seen in the press last Friday our CEO was mentioned in connection with a High Court action, " the email reads. "He is complying completely with the court and hopes that the issue will be resolved in a timely manner. This investigation does not involve IAPI and Seán would not do anything to bring the institute into disrepute."