Almost one third of adults believe that jumping up and down after sex stops a woman getting pregnant, according to a poll that has uncovered alarming ignorance about the facts of life.

The survey, conducted by Gfk NOP for the Family Planning Association, also found that 50 per cent of adults failed accurately to identify a woman’s most fertile time of the month, or knew that sperm could live inside the body for seven days.

Anne Weyman, chief executive of the FPA, said she was “deeply concerned” by the findings and blamed poor sex education at school, with teachers shying from telling teenagers how easy it was to get pregnant.

She said: “In today’s sexualised society, we are bombarded with a multitude of sexual imagery and messages. Yet none of us are born with the facts about sex and reproduction – we are taught them. If this doesn’t happen, myths start getting into circulation and people end up not being able to tell fact from fiction.”

Last week Marie Stopes International said that it had carried out almost 6,000 abortions in January, more than at any time in its 32-year history.

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