The BBC is using anti-terror spy laws to trap licence fee dodgers in Northern Ireland, the Belfast Telegraph can reveal.
It has invoked the Regulation of Investigatory Powers Act (RIPA) to catch viewers evading the £145 charge.
The Act, which regulates the powers of public bodies to carry out surveillance and investigation, was introduced in 2000 to safeguard national security.
But a series of extensions mean it can now be applied to investigate minor offences, including not paying the licence fee.
The BBC confirmed its use of RIPA in Northern Ireland after enquiries from this newspaper.
However, the publicly-funded broadcaster refused to give details of what way and how often it applied the legislation.
The Telegraph's revelation has led to calls for the BBC to justify its use of the controversial powers. DUP MP Gregory Campbell said: "The purpose for which the anti-terror legislation was introduced was pretty clear - the clue is in the name. It should be used for that purpose, and if the BBC is using legislation for a purpose that it wasn't originally intended, then they should explain this to the public."
RIPA was introduced by the Labour government in 2000 to catch terrorists and prevent serious crime. However, in recent years it has been used for minor offences such as littering and making sure parents are sending their children to school.
A document obtained under Freedom of Information legislation confirms the BBC's use of RIPA in Northern Ireland.
It states: "The BBC may, in certain circumstances, authorise under the Regulation of Investigatory Powers Act 2000 and Regulation of Investigatory Powers (British Broadcasting Corporation) Order 2001 the lawful use of detection equipment to detect unlicensed use of television receivers... the BBC has used detection authorised under this legislation in Northern Ireland."
Mr Campbell said it was an "extreme" response by the state broadcaster towards a relatively small number of non-payers.
"It is disproportionate in that they constantly indicate that the numbers of people who are avoiding paying the TV licence fee are very low," he added. "It is difficult to reconcile that with what is quite an extreme legislative process against the small number who don't pay."
The BBC declined to give any details about its use of RIPA. It argued that "maintaining uncertainty" about enforcement practices was part of its strategy to keep evasion to a minimum.
"This uncertainty contributes to the deterrent effect which is an important part of TV Licensing's enforcement strategy," it said.
Emma Carr, director of the Big Brother Watch campaign group, said there was a lack of accountability in the use of RIPA.
"It is clear that in the 15 years since these powers were awarded to councils there has been a huge amount of mission creep in how they are used, as proven by members of the public being snooped on to see if they have paid the licence fee," she said. "A lack of transparency, accountability and oversight of how these powers are used has allowed the use of the powers to reach unacceptable levels.
"It is important that there is a wholesale review of how these powers are being used."
A BBC spokesman said: "Legislation explicitly grants the BBC the right to use these powers to detect unlicensed use of television receivers. We're regularly inspected by independent regulators and have always been open about using this power when there is no other option to help reduce evasion on behalf of the vast majority of the population who pay for their licence."
A TV licensing spokesperson said: "The average evasion rate remains at a low at five to six per cent, meaning 94 to 95 per cent of homes are correctly licensed."