The First half year profits at online gambling firm Partygaming show how badly they have been hit by the US change in the law, as the this high flyer gaming operator posted a pre-tax loss of $47.1m (£23.5m) for the six months to June. Last year it reported a pre-tax profit of $320.5m.

Laws passed in the US last October effectively made it illegal to trade there, hitting the business. But continuing operations were performing “strongly”, the firm added. The City had been expecting worse news as Partygaming’s shares rose almost 19% to 27 pence in afternoon trading on this news.

But the firm’s shares are still less than a fifth of what they were at their peak at the beginning of 2006 when they hovered around 155p but everything changed for the company when last year, President George W Bush signed the Unlawful Internet Gambling Enforcement Act, criminalising the transfer and handling of payments from online gambling and as a direct result, Partygaming withdrew from the US market where it collected most of its revenue and profit.

Despite the huge setback, the group added a record number of non-US new players - up 83% to 403,713 - with its casino business showing the strongest growth in the first half.

Revenue from Partygaming’s continuing business, which strips out the impact of the loss of the US market, showed a 42% increase to $212.5m, up from $149.8m the year before.

Poker still contributed the biggest share of total revenue, with the company’s PartyPoker website leading this arm of the business.