The survey of 1,243 people aged 15-24 found that around 20% did not know that chlamydia can affect female fertility.
In addition, 65% said they did not use a condom when they had sex with a new partner for the first time. Also 90% do no have themselves tested for STIs before starting a new relationship.
The poll was conducted to mark the launch of the government's new campaign, centred on the tagline 'Chlamydia. Worth Talking About'.
Public health minister Gillian Merron stressed that infection with chlamydia can have serious consequences.
‘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,' she said.
She added: ‘The government's 'Chlamydia. Worth Talking About' campaign is designed to encourage normal conversations about sexual health, relationships, contraceptive choices and protection against STIs.'