Have you ever absent-mindedly dunked your cracker into a dip having already done so once?

If so, you are committing the most heinous of dinner party crimes by spreading abundance of germs.

So-called double dipping sees a surge in bacteria, according to research in Harvard’s Healthbeat journal.

It puts to bed a debate started after a 1993 episode of Seinfeld in which George Costanza is called out on the offence at a wake.

After double-dipping a cracker, a disgusted fellow mourner objects: “That’s like putting your whole mouth right in the dip.”

Dr Robert Shmerling, editor of Healthbeat, said: “This research does raise the possibility that a person who is sick might spread a disease by re-dipping a chip.”

Pneumonic plague, TB and Legionnaires’ disease all spread via saliva.

The study investigated the effects of repeatedly dunking a crisp in various substances.

It found that the number of the bacteria varies depending on the type of dip – with salsa accumulating more germs than chocolate or cheese.

Because salsa is not as thick as chocolate or cheese, more of the dip touching the bitten cracker falls back into the communal container taking the dipper’s bacteria-riddled saliva with it.