Andy Murray marched through to his first Wimbledon semi-final yesterday and turned the championships into the hottest ticket in world sport.

Internet sites were awash with offers to buy Centre Court tickets for the men’s final on Sunday, with one seller putting four online last night at an astonishing £20,000 each.

Demand has soared with each Murray victory, driving up prices as tennis fans realised there was a chance that the world No 3 could win his first grand-slam title, underlined by his convincing 7-5, 6-3, 6-2 quarter-final victory over Juan Carlos Ferrero.

Victory over Andy Roddick, the No 6 seed, in his semi-final tomorrow could set up a mouthwatering clash with Roger Federer in the final and the chance of a British man lifting the most coveted trophy in the sport for the first time in 73 years.

Roddick took four hours and five sets to beat Lleyton Hewitt, making it advantage Murray. “I was only on court for about an hour and 45 minutes so it’s not going to take anything out of me physically and I should be 100 per cent for the next match,” the Scot said. “But I realise that if I don’t bring my best game I’m going to lose.”

Fans have been queueing outside Wimbledon for 48 hours to get their hands on tickets for the semi-finals and final, while agencies report that demand is up four-fold. But the prices are higher than ever, with a pair of quarter-final tickets for Murray’s Centre Court match yesterday, worth £170, selling for £6,100.

With the avalanche of demand has come the threat of fraud. Wimbledon authorities are investigating bogus websites charging thousands of pounds for tickets that do not exist. One site under investigation — onlinewimbledontickets.com — is almost a replica of the official Wimbledon website, in the familiar green-and-purple livery, offering Centre Court tickets for the final at £2,499.

A Romanian businessman, who paid more than £11,000 online, is among more than 50 victims, mainly from mainland Europe. The website, with telephone numbers in London and Ireland, takes the money online but does not deliver the tickets. Their phone lines were dead yesterday.

A Wimbledon spokesman said: “We are trying to trace as many fraud operations as we can, in co-operation with the police. This one was particularly effective because the website looks so similar to the official site.

“We have made a lot of progress over the years in stopping the illegal sale of tickets and touting on the streets, but the internet is more difficult to control.” Police have ensured that touts are a rare sight on the streets approaching the All England Club, but the demand for tickets is driving a massive second-hand business, much of it fuelled by Wimbledon debenture holders. They paid £23,150 to secure their Centre Court seats for five years and are allowed to sell them on. There are 2,300 debenture seats, guaranteed until 2010.

If the debenture issue was lucrative for Wimbledon, netting £46 million, it is proving just as good an earner for those seat-holders willing to miss the finals weekend and cash in.

Debenture seats, some with access to the exclusive Centre Court lounges, are on sale all over the internet. Viagogo, the ticket agency, was selling tickets at up to £4,000 for the men’s final last night.

Joe Cohen, founder of Seatwave, said that the rush was triggered immediately Rafael Nadal, the 2008 champion, said that he could not compete because of injury. “At that moment it seems British fans decided Andy Murray had a chance and they wanted to be there,” Cohen said.