A study into marital infidelity has found that longer penises are linked to wives cheating on their spouses.

The study, published in the online Journal PloS One, was led by US and Kenyan researchers, found that every extra inch boosts the likelihood of wives engaging in extramarital affairs.

"We included this variable because of the interest and controversies that surround men's pursuit of penile enlargement ostensibly to sexually satisfy their spouses while women do not necessarily approve of it," the researchers wrote.

"Surprisingly, [having a] spouse [with a] longer fully erect penis was associated with increased likelihood of the women having extra-marital partnerships. From these results, every one inch longer penis increased the likelihood of women being involved in extra-marital partnership by almost one-and-half times," the researchers wrote.

This is apparently because a longer penis increases sexual discomfort. The researchers quoted one of the women in the study as saying, “…some penises may be large yet my vagina is small, when he tries to insert it inside, it hurts so much that I will have to look for another man who has a smaller one [penis] and can do it in a way I can enjoy”.

According to the study, domestic violence and denying a woman a preferred sex position also increased the likelihood of extra-marital relationships.

Meanwhile factors which reduce the likelihood of a wife cheating on her husband are her age (older wives were less likely to cheat), and how sexually satisfied she is.

“Some [men] just take a minute and leaves you there when you are still ‘hanging’… You cannot even tell if this thing is over or still continuing. Sometime we aren't satisfied yet we can't explain it [to our partners]. However, when we get men who can satisfy us, we do not waste such chances," one woman told the researchers.