Britain could look empty during next summer's Olympics. Sales at a leading UK travel business shows demand for holidays in late July and August 2012 is running one-quarter higher than at the same stage a year ago. Meanwhile one of the biggest travel firms in the US has cancelled all tours to Britain for a month leading up to, and including, the Games – partly due to concerns over profiteering by hoteliers.

The dates of the Games, 27 July to 12 August, coincide with the school summer holidays across the UK. The usual effect of a big event, from a royal wedding to the World Cup, is to dampen demand for overseas travel. But Bolton-based Travel Counsellors, which has more than 700 travel agents across the UK, reports sales are 23 per cent ahead of last year.

The figure is significant because it represents real sales rather than merely opinion polls or online searches. The prices being paid by holidaymakers have increased by an average of 6 per cent. Demand is especially strong for the US, Turkey and Cyprus.

Steve Byrne, managing director of Travel Counsellors, said: "There has been a lot of hype about how busy travelling will become as tourists from across the globe flock to the UK for the games, so many of the British public want to make sure they book early to avoid this. We are seeing a surge in sales during the Olympics."

A leading upmarket city-break company has seen sales for next summer rise by 40 per cent, year on year, and reports "a disproportionate spike for departures in July and August".

Cruise passengers traditionally book far ahead, and one specialist agency – The Luxury Cruise Company – has had so many enquiries from people keen to avoid the Olympiad that is has created an online "microsite" devoted to the great Games escape. Alaska, the Mediterranean and European river cruises are selling strongly.

Britain's inbound tourist industry has been hoping for a boost in business over the Olympics. In 2009, the Mayor of London, Boris Johnson, said: "When hundreds of thousands of people come, as they will, to London in 2012, it will inevitably be good for this city and for the tourist economy."

But Jennifer Tombaugh, president of America's oldest tour operator, Tauck Travel, said "We will be cutting capacity to the UK by about 20 per cent next summer." This includes a "blackout" from early July until the end of the Games.

The reasons are complex: some clients would expect toreceive tickets for events at the Olympic stadium; road closures will interfere with "normal" tourism; and there are concerns about high room rates and shortages of high-grade accommodation.

Test bookings made yesterday of Hilton properties in the London area showed almost all "unavailable" for key dates during the Olympics. One exception was the Hilton Hotel at Heathrow airport, where a double room is £349 – more than three times the lowest rate this week of £107.

Case study: Renting out

Ruben de Dios, 30, freelance film-maker

"My partner and I are planning to stay with relatives in Spain, and rent out our apartment in Whitechapel, hopefully for around £1,500-£2,000 a week.

"We experienced the Barcelona Olympics in 1992 and realised when it came to London we needed to get away. We initially looked at estate agents, but wanted to avoid the fee so have decided to do it ourselves. We've approached a couple of websites recommended to us by friends, who are helping people to rent out their properties over the Olympics.

"I bought the place five years ago with my partner, and it was given a rent value of £1,000-£1,200 per month six months ago. But other similar properties out there seem to be charging these high prices, so we're going to set our rent at a similar rate. It's a great location, very near the Stratford site."