Nearly one in four people only sometimes or never use contraception when having sex with a new partner, according to a survey.
A poll of 3,000 people found that the main reason for not using anything is that people "get carried away in the moment".
Almost 10% of those quizzed said they are "not bothered" about using anything, despite the fact that one quarter say they sleep around.
Asked about their sexual encounters, 11% said the majority of them were one night stands and 13% said most were made up of "quick flings".
Another 2% said they mostly slept with strangers.
The survey, from the Co-operative Pharmacy, revealed interesting findings among older age groups.
Among the over-50s, one in four admit to having more than one ongoing sexual relationship.
Some 15% of 144 people aged 51 to 55 surveyed also said they never used contraception with a new partner.
One in three in this age group said they had "slept around" and admitted to unprotected one night stands with strangers.
Meanwhile, of the 174 people aged over 56, some 17% said they never used contraception with a new partner.
This is despite the fact the number of sexually transmitted infections (STIs) in this age group are on the rise across the UK.
Meanwhile, 19% of the 424 people aged 18 to 21 said they had waited until the legal age of 16 to have sex.
Copyright © Press Association 2010
The Co-Operative Pharmacy
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