CIGARETTES may contain traces of pig's blood, an Australian academic says with a warning that religious groups could find its undisclosed presence "very offensive".

University of Sydney Professor Simon Chapman points to recent Dutch research which identified 185 different industrial uses of a pig - including the use of its haemoglobin in cigarette filters.

Prof Chapman said the research offered an insight into the otherwise secretive world of cigarette manufacture, and it was likely to raise concerns for devout Muslims and Jews.

Religious texts at the core of both of these faiths specifically ban the consumption of pork.

"I think that there would be some particularly devout groups who would find the idea that there were pig products in cigarettes to be very offensive," Prof Chapman said today.

"The Jewish community certainly takes these matters extremely seriously and the Islamic community certainly do as well, as would many vegetarians.

"It just puts into hard relief the problem that the tobacco industry is not required to declare the ingredients of cigarettes ... they say 'that's our business' and a trade secret."

The Dutch research found pig haemoglobin - a blood protein - was being used to make cigarette filters more effective at trapping harmful chemicals before they could enter a smoker's lungs.

Prof Chapman said while tobacco companies had moved voluntarily list the contents of their products on their websites, they also noted undisclosed "processing aids ... that are not significantly present in, and do not functionally affect, the finished product".

This catch-all term hid from public view an array of chemicals and other substances used in the making of tobacco products, he said.

At least one cigarette brand sold in Greece was confirmed as using pig haemoglobin in its processes, Prof Chapman said, and the status of smokes sold was unknown.

"If you're a smoker and you're of Islamic or Jewish faith then you'd probably would want to know and there is no way of finding out," Prof Chapman said.

The Sydney office of British American Tobacco Australia was contacted by AAP.

A spokeswoman said a comment would be provided although it was not immediately available.

Originally published as Cigarettes may contain pigs blood