A leading Jamaican drugs tester has claimed the number of failed tests by the country's athletes could be the "tip of the iceberg".

Dr Paul Wright is worried that a recent visit by the World Anti-Doping Agency and a promise to increase drug test funding by the Jamaican Govenrnment could lead to more failed tests.

Recent failed tests have included former 100m world record holder Asafa Powell and his training partner and Olympic relay gold medallist Sherone Simpson.

Powell and Simpson have claimed they took supplements which might have been contaminated by the banned stimulant Oxilofrine.

Former Jamaican Anti-Doping Commission executive director Renee Anne Shirley has also claimed the agency conducted just one out-of-competition test in the six months before the 2012 London Olympic Games.

Dr Wright told the BBC that Jamaica's testing programme - which is due to be discussed at a Wada executive board meeting in Johannesburg on Tuesday - is not up to international standards.

Dr Wright, a senior doping official with Jadco, told the BBC: "The results are not good. This year alone the results really point the finger.

"Remember, all of these results except one were caught by Jadco. The problem is these people were tested positive in competition. What that means is months before you know the date of the test and the approximate time of the test.

"This could be the tip of the iceberg to have so many positives coming in competition.

"What is going to convince me is if there is an out-of-competition test that's unannounced, that includes blood testing and which tests for EPO. Then we can hold up our heads high and say we know there's nothing."

The head of the Jamaican Olympic Association Mike Fennell dismissed Dr Wright's concerns, saying: "I think that's massively overstating it. There's no evidence to suggest that it's the tip of the iceberg."

Jamaica's Minister for Sport Natalie Neita Headley has vowed on increase the country's drugs testing funding following a recent visit to the island by Wada officials.