Internet giants Google and Yahoo! will stop carrying adverts for online casinos, blaming a "lack of clarity" in US regulations.

US prosecutors last month warned companies that running ads for offshore online casinos was equivalent to "aiding and abetting". It is illegal to run an online gambling site from within the US.

Google and Yahoo made the announcement seperately on Friday. Yahoo said the ban would apply to US websites only while Google self-denial hits all its sites worldwide. The change is likely to come in at the end of this month, according to the New York Times.

David Carruthers, CEO of betonsports.com, told the paper: "I urge these search engines and other service providers to stand up for themselves and challenge these pressure tactics by federal prosecutors."

Some legal observers believe adverts for online gambling could be protected under free speech rights.

The World Trade Organisation recently ruled that the US ban on online gambling was in breach of international trade law. ®

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