SPYING on left-wing groups by a secret Metropolitan police squad was not justified and the unit should have been closed down, a landmark report has found.

Findings from the first part of a mammoth public inquiry into undercover policing were published on Thursday, covering the activities of the shadowy Special Demonstration Squad (SDS) between 1968 and 1982.

The inquiry will go on to look at the activities of the unit until 2008, examining scandals over women being deceived into sexual relationships, the use of dead children’s names without their families’ consent and spying on justice campaigns including that for Stephen Lawrence.

Chairman John Mitting concluded that if details of what the SDS was doing had been made public in the 1970s, the unit would have been “brought to a rapid end”.

The squad required annual authorisation and funding approval from the Home Office, and in 1976 a group of senior police officers found it should continue work with a minimum of 12 undercover officers.

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But Mitting found that key issues had not been considered, including long-term undercover deployments meaning intrusion into the personal lives of many hundreds of people, including entering their homes by deception.

Officers accepted positions of responsibility within the groups they were infiltrating and became involved in organising political activity, and their use of dead children’s identities should have been referred to the highest ranks of the Met and the Home Office, he concluded.

Mitting said: “If these issues had been addressed, it is hard to see how any conclusion could legitimately have been reached which would not have resulted in the closure of the SDS.”

He said that the infiltration of only three of the groups that were targeted at the time could be justified – (Provisional) Sinn Fein and two others that have not been publicly named.

“The principal, stated purpose of the SDS was to assist uniformed police to control public order in London,” Mitting found.

“Long-term deployments into left-wing and anarchist groups did make a real contribution to achieving this end, even though this was or could have been achieved to a significant extent by other, less intrusive, means.

“The question is whether or not the end justified the means.”

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He went on: “I have come to the firm conclusion that, for a unit of a police force, it did not; and that had the use of these means been publicly known at the time, the SDS would have been brought to a rapid end.”

Mitting said among 2600 documents from between April 1975 and May 1978, 1400 were about people’s identities and lives; 1200 were records of the meetings and activities of groups that were spied on, and 200 were reports on forthcoming events that might have an impact on public order in London.

He said: “It is a striking feature of the reporting of almost all SDS undercover officers that it contained extensive details about individuals – their political views, personality, working life, relationships with others, and family and private life.”

This is the first report to come from the Undercover Policing Inquiry, that was set up in 2015 by then-Home Secretary Theresa May in response to outrage over various tactics used by undercover officers.

In the foreword to Mitting’s report, he said the impact of the deceitful relationships, the use of dead children’s names and spying on justice campaigns were best addressed once all the evidence is in.

The inquiry, which has so far cost £64 million, is expected to finish in three years’ time.

Mitting also concluded that the absence of targeting of right-wing groups at the time was not due to political bias, but the fact that those groups were already sufficiently covered.

He said: “The fact that in this period no decision was made to infiltrate right-wing groups did not result from political bias on the part of those responsible for targeting, but from the belief that existing coverage sufficed and through concern about the risk of violence which such a deployment might pose.”

Lord Peter Hain, who was part of anti-apartheid groups that were targeted by undercover officers, said: “The report reveals clear political responsibility for illegitimate undercover police operations targeting anti apartheid and anti racist groups going right up to Prime Ministers of the day.

“However in stating ‘that no decision was made to infiltrate right wing groups did not result from political bias’ is an astounding endorsement by Sir John Mitting of the very political bias the police and security forces displayed at that time.

“The fact is the police and security forces were consistently on the wrong side of history and the inquiry has just ignored that.

“It is reprehensible that Sir John Mitting does not take a stand on the very evidence of discriminatory policing his Inquiry uncovered.”