The US ambassador to the Philippines has apologised for his controversial remark that 40 percent of male tourists visit the country for sex, according to the foreign department.

Harry Thomas sent the apology through a cell phone text message to Philippine Foreign Secretary Albert del Rosario on Friday, a spokesman said.

In a statement, the US embassy confirmed that Thomas had expressed "deep regret" for his remark.

Last month, Thomas sparked a furore when he said: "Forty percent of foreign men who come to the Philippines, including from the US, come for sex tourism."

Government officials quickly disputed the claim, complaining that the envoy's remark had hurt the Philippines' image.

"I am sending you a response expressing regret for my comments. I should not have used the 40 percent statistic without the ability to back it up," the spokesman quoted Thomas as saying in his text message.

The ambassador's claim about sex tourists came amid Philippine government attempts to revitalise the country's tourism industry, which for years has lagged behind other Asian countries.

The Philippines recorded an all-time high of 3.52 million visitors last year and the government is aiming for tourist arrivals of six million by 2016.