Fifa has launched an investigation after the BBC discovered touts were selling illegal tickets for England's World Cup games for up to £900 each.
With Fifa selling the same tickets for £68, it represents a 1,000% mark-up.
Representatives of onlineticketshop.com offered a reporter tickets to England's match against Sweden for £695 and £895.
Fifa has said all tickets sold by online tickets brokers are invalid and may lead to holders being refused admission to stadiums in Germany.
Under anti-hooliganism laws, it is also a criminal offence for anyone in the United Kingdom, other than official bodies, to offer to sell tickets for England games.
Onlineticketshop.com claims on its website to be registered in the United States which might provide it with a loophole to escape prosecution in the UK.
The investigation by BBC Radio's Five Live Report also found another six internet sites selling illegal England World Cup tickets.
"We are going to be investigating these companies," a Fifa spokeswoman said.
"We would advise fans not to buy World Cup tickets from online ticket sellers."
Onlineticketshop.com is a British company owned by Terrence Shepherd, who lives in south-east London.
Its latest accounts show it has a turnover of £3.5m.
BBC Five Live's investigation discovered Mr Shepherd previously ran Sports Mondial, which was hit by court sanctions after it was accused of selling non-existent tickets for Euro 2004.
The company was also taken to court in Australia by the National Rugby League in 2003.
It emerged during the case that Mr Shepherd's company had obtained tickets for a tournament in Australia by applying for them using more than 100 fictitious names.
The following year, Uefa successfully obtained an injunction against Sports Mondial, accusing it of selling tickets to Euro 2004 in Portugal without permission.
The consumer watchdog in Portugal issued a Europe-wide warning that the company was selling tickets it did not have.
Fans eventually lost thousands of pounds when the tickets failed to materialise.
Mr Shepherd failed to respond to several attempts to contact him.