Google (NASDAQ: GOOG - News) is allowing gambling advertisements in its search results in Britain - for the first time anywhere in the world since a self-imposed moratorium in 2004.

Industry experts say the search engine, which welcomed the Queen and Duke of Edinburgh to its London offices on Thursday, could generate more than £100m ($173m) in revenues from rule changes, which come into effect on Friday. The business commands a 70 per cent share of the paid search advertising market in the UK.

Google has been reviewing its gambling advertising policy "to ensure it is as consistent as possible with local business practices", said James Cashmore, industry leader, entertainment and media, at the company. "We hope this change will enhance the search experience for users and help advertisers connect with interested consumers."

Google banned gambling advertisements when the US Congress cracked down on the industry in 2004.

Online gambling companies welcomed the lifting of the ban, which follows the UK Gambling Act's removal of prohibitions on television advertising of casino and bingo gaming, which came into force in September 2007.

"We rely a lot on advertising as our shop window," said Clive Hawkswood, the chief executive of the Remote Gambling Association, whose members include Ladbrokes, PartyGaming, 888 and other online gaming sites. "Our products are online so the marketing will be using Google a fair bit."

According to figures from Nielsen, the market research group, casino, lottery and bookmakers are collectively the third largest advertisers in online display ads,both by number of campaigns and share of spending.

"The fact they are third behind mobile phone operators and automotive manufacturers shows they are spending a lot of money on online advertising," said Alex Burmaster, European internet analyst at Nielsen. "Perhaps Google are going to hit the jackpot."