The maximum time for great sex is 13 minutes, according to a survey.

Those quizzed said less than three minutes is "too short" while up to seven is "adequate".

Sex lasting seven to 13 minutes was the most desirable. Beyond that, it is "too long".

The US report in the Journal of Sexual Medicine aimed to dispel the belief that good sex should go on for a long time.

Researcher Dr Eric Corty said: "The results will be useful in treating sexual concerns and sexual dysfunctions."