Key Points:

Three controversial New Zealanders undoubtedly spied for Russia, the author of a new book says.

And Russian President Vladimir Putin may have been in the country on assignment for the KGB in the Cold War 1980s.

Aucklander Graeme Hunt, whose book Spies and Revolutionaries is released this week, said his research found Bill Sutch, Ian Milner and Paddy Costello were spies.

"The book for the first time removes any doubt about the loyalty of the three quite prominent New Zealanders," he said.

He expected opposition, particularly from Sutch supporters, who refused to believe Sutch was anything other than a hard-working public servant and not a communist sympathiser.

Sutch, Secretary of Industries and Commerce until forced to retire in 1965, was tried for spying in 1975.

He walked free after a five-day trial, largely because the jury was not told details of the "secrets" he was purported to have passed to the Russians.

Hunt said his research had shown Sutch and Milner were "fellow travellers" - communist sympathisers who were not paid up members of the Communist Party but who "were acting in the interests of Russia".

He said Sutch collected dossiers on people which could have been extremely damaging.

"It was the sort of information the Russians routinely collected, not just from New Zealand but from right around the world, which they could use for blackmail purposes, to influence people in high places, to provide a dossier of information which could be used at some time in the future."

The book, which covers the history of spying from the 1860s to the Israeli passports scandal in 2004, also suggests Mr Putin may have been here when David Lange ordered Soviet diplomat Sergei Budnik to leave in 1987.

"A man bearing a striking resemblance to [Mr Putin] was in New Zealand in 1986 for the inquiry into the sinking of the Russian cruise ship Mikhail Lermontov in the Marlborough Sounds."

Hunt said that while Sutch was well known in New Zealand, Costello had an international reputation and his spying activities were well documented in the files of the KGB, the Russian secret police.

Costello was born in Auckland in 1912 but when he was 20 he enrolled at Trinity College at the University of Cambridge in England.

He was to become the most important New Zealand spy recruited by the Soviet Union, Hunt said.

He joined a secret communist cell at Trinity College after being recruited by Anthony Blunt. He knew Kim Philby, Guy Burgess, Donald Maclean and John Cairncross - "that quintet of horrible spies, the so-called tight five of the Cambridge spies in England". Hunt said Costello, who spoke Russian and a host of other languages, was listed in a 1953 KGB list as a "valuable agent" in Paris.

The Security Intelligence Service had no doubt he was spying for the Soviet Union.

Ian Milner, son of Frank Milner, headmaster of Waitaki Boys High School and a former Rhodes Scholar, was named as one of six suspected spies in a report to Parliament in 1955.

His discussions with the Russians had been closely monitored.

The report said he had probably passed secrets to the Russians when an official in the Department of External Affairs in Canberra in 1945 and 1946.

He enrolled at Oxford University's New College in 1934.

His Rhodes scholarship was the epitome of deception to satisfy the aspirations of his imperialistic father.

He joined the illegal Communist Party in Australia in 1941 and was active in a variety of communist fronts, "which left little doubt where his sympathies lay", Hunt said.

"There is no romanticism attached to communism," Hunt said.

"It has completely fallen from grace. It represents oppression, deceit, destruction and lies and the ruination of many economies."

He said the brand was worthless.