The Snowden revelations harmed GCHQ’s ability to monitor the communications of crime lords, leading to some vanishing off the grid and the abandonment of other surveillance operations, sources have told a British newspaper.

Intelligence officers claim to be blind to more than a quarter of the actions of the UK’s worst crime gangs following changes by crooks in their communication methods, which spooks attribute to leaks by the former NSA contractor, the Daily Telegraph reports.

Spy bosses previously warned that the Snowden leaks affected their efforts to track terrorists, claims which are disputed by privacy activists. The Daily Telegraph, citing unnamed “senior security officials”, claims that GCHQ’s role in combating serious and organised crime has also been harmed.

Communication suppliers – historically willing facilitators of wiretapping – are “refusing to hand over evidence on the likes of drug smugglers or fraudsters” because they do not pose a “direct threat to life”, Telegraph security editor Tom Whitehead writes.

One unnamed major drug smuggling gang has supposedly been able to operate “unimpeded for the last year” after changing their operations last autumn, throwing GCHQ off the trail in the process. Plans to track other groups have either been abandoned early or shelved entirely because of concerns that formerly reliable bugging tactics are too easy to spot and might do more harm than good because they would act as a tip-off to targets that they are under surveillance.

A senior security official said: “Snowden has been very damaging to our work. We have specific evidence of where key targets have changed their communication behaviour as a direct result of what they have read.”

“They have moved to more secure forms of communication and we have been unable to assist the NCA (National Crime Agency). It takes longer to help law enforcement and because we only focus on the most serious, the top end networks, then the impact they have in the mean time is multiplied,” the unnamed official added.

Edward Snowden stole thousands of classified files that were leaked through his media collaborators, exposing the mass surveillance of Americans by the NSA as well as the tools and techniques of GCHQ. Spy bosses have repeatedly complained that terrorist suspects and child abuse networks had “gone dark” as a result of Snowden’s disclosures. Law enforcement figures on both sides of the Atlantic have complained that plans by Apple and Google to build improved encryption into smartphones is a gift to criminals, particularly terrorists and paedophiles. This same argument has now been extended to cover drug lords.

GCHQ works with the National Crime Agency to fight the most serious organised crime groups, including drug smugglers, human traffickers and child abusers. Gangs have moved to more secure communications as a direct result of the Snowden leaks, it's alleged.

“We have techniques that need to be protected,” the source told the Telegraph. “The choice is not to pursue a network and we have decided not to press ahead where there is a possibility of being detected.”

“Experts needed up to six weeks to ‘deliver the magic’ when tasked with tracking and monitoring targets”, the Telegraph reports, adding that the time need to crack communications had effectively trebled over recent months.

The reaction from privacy and security experts to previous gripes by spies about more secure communication methods being more widely used and available has been to respond that spies had brought these changes upon themselves. The latest gripes about serious crims improving their comms security had provoked a similar reaction, as well as scepticism about whether the claims can be taken at face value.

Prolific natsec tweeter Spy Blog said:

Struggling to understand #GCHQ @NCA_UK going dark claim http://t.co/bZvB1tITEE How is " deeper surveillance" *easier* for gangs to detect ? — Spy Blog (@spyblog) December 22, 2014

Others, such as security consultant Gareth Niblett, are puzzled by the “six weeks to de-cloak comms” claim.

@CasparBowden have GCHQ just suggested criminals should change comms approach every <6 weeks to avoid their 'magic'? — Gareth Niblett (@garethniblett) December 22, 2014

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