According to the data collected, men who were infertile had an average length of 4.92in compared to fertile men with 5.27in.

Study leader Dr Austen Slade of the University of Utah, Salt Lake City, said: ‘It may not be a striking difference but there was a clear statistical significance.

‘It remains to be determined if there are different penile length cut-offs that would predict more severe infertility.’

Dr Slade said shorter penises could hint at problem with fertility but added it was nothing to be worried about.