Once in the UK, visitors spent more too, shelling out £6.6b - an increase of 6% over the same period in 2005.
Commenting on the figures, VisitBritain's chief executive Tom Wright said: "Nearly 15 million international visits is a great start and another record for Britain's visitor economy. However, the industry continues to face challenges and increasing competition from rival destinations."
"To build on this success, we need to continue to woo valuable American and Japanese visitors, explore new markets and ensure that this country offers quality, value-for-money experiences and unrivalled welcome," he added.
Tim Helliwell, Barclays' expert on the hotel and leisure sector said: "The UK hotel sector continues to perform reasonably well, particularly in London, which is the driving force and benefiting from healthy visitor numbers from overseas. Provincial hoteliers face more of a challenge however to lure both domestic and international travellers. The outward-bound numbers show that Brits are increasingly looking to spend their holidays abroad, while the capital continues to draw foreign visitors.
"US visitor numbers are up, but there are indications that this is largely due to business, rather than leisure travellers, who may have been deterred by the recent weakening of the dollar and the increase in long-haul flight costs."
Visitor numbers from North America were up 9% to 2.1 million, while 9.8 million visitors arrived from Western Europe - an increase of 6% over the first six months of 2005. Residents from the rest of the World accounted for 2.96 million visitors, a rise of 5%.
By Matthew Batham