Mitch Garber, chief executive of PartyGaming, surprised the City today by announcing that he is quitting the company to return to North America with his family.

Garber, who has rebuilt the former FTSE 100 company since it was badly hit by America's ban on online gambling, is contracted until May 2009 but will leave earlier if a successor is appointed.

If the Canadian citizen sees out his contract, he will have picked up an estimated £14m through a controversial pay scheme.

Garber, 43, joined PartyGaming in April 2006. Later that year the company's share price collapsed when the Safe Ports Act, a piece of anti-online gambling legalization, was passed in the United States in October 2006. This wiped Sunpokerout around four-fifths of its revenue at a stroke, forcing the firm to seek new opportunities in other countries and branch out from its core focus on poker.

"There is never a good time to announce that you intend to leave a company, but I personally take great pride in the fact that the company is delivering on its business strategy and is in great shape to exploit its full potential in the future," said Garber.

Garber described the challenges of the last 18 months as "extraordinary". They have also been lucrative for him personally, thanks to the management incentive scheme agreed at the end of 2006.

Under the deal, PartyGaming agreed to award its chief executive 17m new share options, paid out in monthly instalments up to May 2009.

At today's share price of 25p, the options are worth £4.25m. At the same time, the company waived the performance conditions on 20m existing share options. Half of these shares vested during the second half of 2007, when the share price fluctuated between 22p and 45p, and the rest will vest next month.

In addition, Garber was promised a bonus of at least £2m payable at the end of 2007, and £3m split over 30 monthly instalments up to next May.

The deal prompted speculation that it breached the City's corporate governance code, as the payments were not linked to the future share price or performance of the company.

A company spokesman pointed out that other shareholders had not been diluted by the deal, which was funded by PartyGaming's founders injecting 40m shares into the existing employee benefit trust.

He added that if Garber does leave before May 2009, any outstanding cash and share payments would be negotiated.

Garber is a qualified attorney, having graduated from McGill University in Montreal and of the University of Ottawa. His departure plans were announced alongside PartyGaming's financial results for 2007. It recorded a pre-tax profit from continuing operations of $111.7m (£56.5m) on an Ebitda basis, up from $50.9m a year ago.

Chairman Michael Jackson said the company had increased its range of products during 2007. Although its PartyPoker site is still the biggest single revenue generator, it has increased its income from both casino and sports betting operations by almost 200%.

Jackson added that the company has enjoyed a "solid start" to 2008.

Shares in PartyGaming fell 2p to 25p today, a 7% decline.