News of the World management instructed a private detective to join the NUJ and obtain a press card so he could "become a journalist" as a cover, according to the union's submission to the Leveson Inquiry.
The NUJ says the man was told to "stop" being a private detective and instead "became a journalist" in the wake of the arrest of NoW royal reporter, Clive Goodman.
The union describes it as "a breathtakingly cynical move" given News International's refusal to recognise the NUJ, according to the latest issue of the NUJ magazine The Journalist.
It says the man's work remained unchanged - surveillance of celebrity "targets"- some of whom have emerged as victims of phone hacking.
News International derecognised the NUJ when it left Fleet Street for Wapping in 1986 and set-up its own staff association.
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