FEARS were raised last night that a notorious undercover copper who spied on trade unionists is still at large when the Met refused to deny he was still in service on the grounds of “health and safety.”

Slippery Mark Jenner posed as a joiner in 1996 and became active in construction union Ucatt.

But Metropolitan Police bigwigs spurned a freedom of information request asking if the former spy was still on duty, saying they would not “confirm or deny” any details of his activities.

In a lengthy dossier excusing their decision to keep shtum, the Met cited the need to protect “personal data” as well as the potential for “health and safety” breaches.

“It is deeply cynical for the police to be using personal data as an excuse to withhold information, when they had no hesitation to distribute workers’ personal details to blacklisters and ruin their lives,” said Ucatt acting general secretary Brian Rye.

The news came as a Tory MP told a parliamentary debate on new snooping powers that spying was “an example of British values.”

A bosses’ database of blacklisted construction workers uncovered in 2009 revealed a number of entries that could only have been supplied by police officers.

Unions suspect that forces passed on intelligence gathered by undercover officers including records of targets’ families and day-to-day activities.

“The police’s continued refusal to answer questions about their role in the blacklisting of ordinary construction workers is reprehensible,” said Mr Rye.

“Everyone who had their lives blighted by blacklisting deserves the complete truth.

“That will only be achieved through a full public inquiry into this disgusting practice.”

Shortly before the election, the government announced a judge-led inquiry into undercover policing headed by Lord Justice Pickford, but it remains unclear whether it will cover blacklisting and union infiltration.

Calling himself Mark Cassidy, Mr Jenner was active between 1995 and 2000 in rank-and-file union events and reportedly even chaired meetings during his undercover years.

He also indulged in a five-year live-in relationship with a woman he was spying on.

Anti-police surveillance campaign group Netpol co-ordinator Kevin Blowe said it would be “staggering” and “totally reprehensible” if he was still employed as a copper.

Mr Blowe said it was likely that surveillance tactics deployed by Mr Jenner’s unit, the Special Demonstration Squad (SDS), were still being used elsewhere in British policing.

“The police have very strongly pushed the idea that this happened in the past,” he told the Star.

“There’s so much focus on the SDS that it’s quite frustrating for those of us who suspect that this still continues.”

He added that there had been “equivocation” from the Met over whether sleeping with targets was still considered a legitimate tactic.

The outcry came as Home Secretary Theresa May told MPs that the government would propose new draft surveillance powers in the autumn.

She said that the “snoopers’ charter” proposals blocked by the Lib Dems during the last parliament were “too wide-ranging” and would be tightened up.

Former government lawyer Victoria Prentis, who was elected a Tory MP last month, said that Britain was “lucky to have” its spies.

“They have been proved repeatedly to be both efficient and decent and a great example of the values we hold so dear in this country,” she said.