Britain's Food Standards Agency has issued a nationwide warning about misleading and illegal claims on the labels of New Zealand honey, after tests revealed many manuka honey products have none of the claimed active properties, Radio New Zealand reported on Sunday.

Some of the companies selling mislabelled honey are New Zealand producers and some are foreign. But even the most reputable New Zealand honey producers now face heightened surveillance in Britain.

The honey industry is estimated to be worth 120 million NZ dollars (96 million US dollars) a year in New Zealand.

But tests by reputable British, Chinese and Singaporean laboratories reveal many manuka honey products have none of the claimed active properties - some of the honey is not even manuka - prompting industry leaders to demand a crackdown on "potentially huge fraud".

The New Zealand Unique Manuka Factor Honey Association, which represents New Zealand manuka honey processing companies, said it is well known that New Zealand sells more manuka honey than it produces, but the industry has failed to deal with that.

The head of the association John Rawcliffe said a crackdown on the fake manuka had to happen.

He said after much delay, his organization has come up with a testing regime that will help consumers identify the real thing from a fake.

A spokesperson of the Ministry for Primary Industries said it will come up with a definition of manuka honey that is internationally agreed on and backed up by robust science.

"It's important for industry to work with MPI and come up with some agreed and reliable standards for consumers," said the spokesperson.