The country's leading expert in infectious diseases, Dr Susan Clarke, has warned that many sexually active teenagers are unaware that they have an STD and are infecting unsuspecting partners.

The consultant at Dublin's St James's Hospital said recent surveys have shown that as many as 15%, or one in six, of teenagers under 18 years of age who have been screened at clinics have been found to have an STD.

Clarke said that major spending is needed to tackle the problem.

St James's Hospital runs six clinics a day but is still "turning people away", she said.

Clarke's comments will also have major implications for the government's emergency legislation on statutory rape.

Her remarks highlight the massive difficulty facing the all-party Oireachtas committee in achieving any consensus on new law in this area.

She described the issue of dealing with teenagers under the legal age of consent as a "legal nightmare".

She added that, legally, teenagers under the age of consent who present themselves at a clinic "should be reported to the gardai".

Under the newly introduced emergency legislation, a 17-year-old boy is guilty of statutory rape if he has consensual sex with a girl under that age, but she is exempt from prosecution.

The top consultant warned the Oireachtas health committee that many young people, especially men, do not exhibit any signs that they are carrying an STD, such as chlamydia, syphillis, gonorrhea and genital warts.

She said that the gender divide in infection cases was equally split between males and females.

"Many people do not realise that they are at risk of having a sexually transmitted disease. Half of the hospital's patients who have infections would not have perceived themselves as having a highrisk contact, " she said.