Blunders in the use of controversial snooping powers meant 13 people were wrongly arrested last year on suspicion of being paedophiles.

Another four individuals had their homes searched by detectives following errors in attempts to access communications data, a watchdog revealed yesterday.

Other mistakes also included people unconnected to an investigation being visited by police and delayed welfare checks on vulnerable people including children whose lives were at risk, said the Interception of Communications Commissioner.

Blunders in the use of controversial snooping powers meant 13 people were wrongly arrested last year on suspicion of being paedophiles

Sir Stanley Burnton also warned that jail staff were giving dangerous prisoners the chance to commit serious crimes by failing to listen to all their phone calls or by listening to them too late.

The wrongful arrests were among 23 serious mistakes made as the police and security services acquired 761,702 items of confidential web and phone data.

Communications data includes the ‘who’, ‘when’ and ‘where’ of a phone call, text or email but not the content and bank or credit card details.

A large proportion of the errors involved an internet address which was wrongly linked to an individual.

Of the 23 serious mistakes, 14 were human errors and the other nine ‘technical system errors’.

Sir Stanley’s annual report said: ‘Any police action taken erroneously in such cases, such as the search of an individual’s house that is unconnected to the investigation or a delayed welfare check on an individual whose life is believed to be at risk, can have a devastating impact on the individuals concerned.’

Overall, 1,199 communications data errors were reported to the watchdog in 2015 - an increase of 20 per cent on the previous year.

Nearly 94 per cent of all the requests were made by police and law enforcement organisation and just under 6 per cent by the intelligence agencies.

The Investigatory Powers Bill was introduced in the aftermath of damaging leaks about security service snooping by Edward Snowden (above), the computer specialist who worked at a US intelligence centre

The watchdog also received 62 reports of errors related to the 3,059 interception warrants, which allow the police and security services to access the content of calls, emails, and other messages.

In addition, the commissioner inspected prisons and identified some instances where not all of the calls made by inmates were being listened to, or recordings of the conversations were destroyed before they were played back.

This meant that details of crimes discussed in phone calls from cells might be missed.

Interception of communications is mandatory for high-risk Category A inmates and those on an ‘escape’ list. Prisoners posing a significant risk to children, sex offenders and people convicted of harassment may also be targeted.

The report said: ‘This is of concern because a significant piece of intelligence could be missed completely or not reacted to promptly, leading to a serious incident occurring which may have otherwise been prevented.’

Sir Stanley was also concerned that calls in foreign languages were not being monitored adequately.

Farcically, prison guards were listening to a large number of calls made by some of the 10,000 foreign criminals in jails in England and Wales without them being translated.

The report said: ‘Inspections revealed that staff were being directed to listen to a large number of calls made in foreign languages but were not being provided with any guidance as to whether the calls should be translated.

‘Consequently no benefit was being derived from the monitoring, which undermines the necessity and proportionality for it as the exercise cannot meet the objective for which monitoring was authorised.’

Meanwhile, a separate report, also released yesterday revealed that security services made nearly double the number of mistakes using intelligence powers in 2015 than in the previous year.

Almost all of the 83 errors in 2015 led to an intrusion into privacy ‘to some degree', the Intelligence Services Commissioner found.

The reports were published as the Government tries to push through what has been described by critics as a ‘turbo-charged snooper’s charter’.

Critics have warned that there is a risk the Investigatory Powers Bill will ride roughshod over people’s privacy using recent terror attacks to justify greater surveillance powers.

The Bill was introduced in the aftermath of damaging leaks about security service snooping by Edward Snowden, the computer specialist who worked at a US intelligence centre.

Ministers insist it is an attempt to bring all new and existing spy tactics used by the intelligence agencies in the digital age under one piece of legislation.

Last night, a Government spokesman said: ‘Although errors in acquiring communications data occur very infrequently, any error in these circumstances is deeply regrettable - especially when it has significant consequences.

‘The Interception of Communications Commissioner made a number of recommendations to improve processes and prevent errors from occurring. All public authorities who received recommendations will be considering very carefully how to put them into practice.