More than a third of people have had a condom come off, or split, during sex, according to a study in Britain.
Of the 497 people surveyed by NOP World for sexual health charity fpa, formerly the Family Planning Association, 64 percent said they did not know why that happened or what had gone wrong.
Some 43 per cent of those questioned said men and women didn't talk about condom sizes because they were embarrassed discussing penis size. Of the nearly 500 adults between 18 and 35 that were surveyed, a quarter were also not aware that condoms came in different lengths and widths.
"Men come in different shapes and sizes and so do condoms," said Toni Belfield, fpa's director of information.
"Poor use of condoms can have devastating consequences on people's sexual health.
"Recent figures show the UK has the highest ever number of new cases of chlamydia and continued high rates of unwanted pregnancies."
The charity called on the government-run National Health Service (NHS), the largest distributor of free condoms in Britain, to provide a wider variety of condom.
Belfield said: "Problems such as condoms splitting or coming off are directly related to people choosing the wrong size and shape, or not using them correctly. When this happens, people lose trust and confidence in the method.
A spokeswoman for the Department of Health defended the government's record on prevention of sexually-transmitted diseases, noting that it had invested 300 million pounds (USD 572).