Young people are responsible for two thirds of chlamydia cases
One in five people do not know that chlamydia can damage a woman's fertility, a government commissioned survey shows.
And two-thirds of the 2,000 adults questioned said they do not use a condom when they have sex with a new partner for the first time.
Ministers want better uptake of screening for the sexually transmitted infection among 15-24 year olds.
In 2008, almost 210,000 people were diagnosed with chlamydia in the UK.
Around three-quarters of those were in the screening target age group.
Chlamydia screening was first introduced as a series of pilots in 2003 and was rolled out nationally four years later.
In November last year, the National Audit Office said the programme had wasted millions of pounds because the NHS had duplicated effort and failed to test as many under 25s as it should have.
Often known as the "silent infection", chlamydia commonly shows no symptoms.
But left undetected it can cause infertility.
Testing, which can be offered in GP surgeries, pharmacies and sexual health clinics, involves taking a urine sample.
Of young people questioned for the Populus survey, 14% said they were worried about accepting a chlamydia test because they were not sure what was involved.
Launching a campaign to raise awareness of screening, public health minister Gillian Merron, said the infection could have serious consequences and they wanted to encourage normal conversations about sexual health and contraception.
"Young people sometimes feel too embarrassed to ask for the test even though they know it is one of the most common sexually transmitted infections in the UK."
The survey also found that 41% of parents of 15-24 year olds have not spoken to their children about any sexually transmitted infections.
And one in five believe their son or daughter is not the type of person to sleep around and 14% believe he or she is not having sex at all.
But 76% are aware that chlamydia is widespread among young people.
Children's minister, Dawn Primarolo, said: "We want parents and professionals to encourage young people to have open and frank conversations about contraception and sexual health and to help remove the stigma associated with sensitive problems such as chlamydia."
A spokesperson from sexual health charity, Brook, said: "As chlamydia often has no symptoms people may not be aware that they have it.
"If left untreated it can lead to infertility and other complications - however it is really easy to test for and treat.
"Brook welcomes the latest strand of the Department of Health's 'Sex. Worth Talking About' campaign to promote positive sexual health messages to young people and to encourage open conversations - this is what young people tell us they want."