Tasmanian parents are not dumping disposable nappies properly, with a survey finding they make up a quarter of the state's litter.

A survey by Keep Australia Beautiful sampled litter twice at 76 sites around Tasmania over the course of a year.

Chief executive Peter McLean said dirty nappies left to rot were unhygienic and extremely unpleasant.

"We're picking up roughly four litres of volume of miscellaneous litter and 25 per cent of that in Tasmania is actually made up of dirty disposable nappies," he said.

"It's certainly disgusting, it's smelly, it's also an eyesore and it's also a public health issue as well, apart from the fact that it takes hundreds of years for a nappy to break down at the same time."

He said parents do not consider the fact that it will be their children who are forced to clean up environmental damage caused by nappies down the track.

Mr McLean said disposable nappies were particularly troublesome.

"Disposable nappies are now so absorbent that even small varieties swell to become relatively large and heavy," he said.

"There's an irresponsible segment of society who are doing the wrong thing and they really need to pick up their act.

"It's not hard, don't be lazy, put it in a rubbish bag, tie it up nice and tight in your car, and then you can dispose of it at a roadside bin, perhaps in a service station, or you can just take it home and pop it in your normal household waste."