Lie detector tests monitoring the behaviour of released sex offenders across England and Wales have begun this week, amid calls for the technology to be used more widely in police investigations.

The tests are now compulsory for high-risk sex offenders let out on licence.

Seven probation officers and four police officers have completed training to operate polygraph machines that measure changes in pulse, skin conductivity and breathing in order to assess whether individuals are telling the truth.

The probation officers and police constables have undergone an 11-week training course coordinated by Don Grubin, professor of forensic psychiatry at Newcastle University. The first tests by probation officers, under supervision, were carried out in London and Leeds on offenders this week; officers will begin operating on their own in the coming months.

The Ministry of Justice's enthusiasm for polygraph machines follows a successful trial report in 2012 which concluded that it "increased the chances that a sexual offender under supervision in the community will reveal information relevant to their management, supervision, treatment, or risk assessment".

Convicted sex offenders are being tested every six months; if they fail then they will be subjected to more frequent assessments. "No one can be recalled to prison simply for failing a test," Grubin told the Guardian, "but if they make disclosures about breaching the terms of their licence then they can be recalled.

"There are so many misconceptions about polygraph testing. People say it's not 100% accurate and the error rate is about 10%. Then you make judgments based on that. There are very few tests that are 100% accurate. Polygraphs have a good accuracy rate. Every study has shown marked increases in disclosures."

Hertfordshire and South Yorkshire police are also running separate pilot projects testing suspects accused of downloading indecent images of children. Their lie detector tests are used to assess how thorough the examination of a suspects' computer should be.

"The aim is resource management," Grubin said. "If someone is deemed to be low risk, and has not been trying to meet children then their computers are subject to a summary review rather than a full forensic examination which can take up to a year."

Part of the risk assessment is through administering a polygraph test; if they pass and make no new admissions then that will influence the police action. "It won't affect any charges," Grubin added, "but it can focus resources on those who are higher risk."

Grubin said he has received expressions of interest from other police forces who are interested in lie detectors for investigations and held discussions with those who think it could be useful in the pre-employment screening of those who work with children.

The Crown Prosecution Service, the MoJ and police all stress that results of tests will not be used in court as evidence of whether or not a crime has been committed.

The Criminal Cases Review Commission says it has received the results of lie detector tests in applications from those seeking to overturn convictions but cannot take them into consideration because they are not admissible as evidence. Among those who have been tested in the hope of proving their innocence is Jeremy Bamber, who was convicted in 1986 of murdering his adoptive family. The website supporting his campaign for freedom says he "passed emphatically".

Many scientists are sceptical about the effectiveness of polygraph testing. Dr Síle Lane, campaign director at Sense About Science, condemned the introduction of lie detectors. "They are not accurate," she said. "They have been shown time and time again not to be able to detect lies. If they work at all it is as a deterrent effect. It's because someone has been told an untruth that they work.

"When police forces are using them to make decisions about someone's liberty in the justice system, that's appalling. The Ministry of Justice needs to answer some questions about why they are spending this money."

A report by the British Psychological Society in 2004 concluded that: "The results of better quality research studies demonstrate that while the correct classification of deceivers can sometimes be fairly high, incorrect decisions about who is or is not being deceptive occur at rates that are far from negligible. Use of countermeasures may well result in deceivers not being detected."

But while there is resistance to the use of polygraphs in many western European countries, they are now commonly used for police investigations and security vetting in central and eastern European states such as Latvia, Lithuania, Poland, Romania and Slovenia. MI5 is rumoured to have used them in the UK.

Lie detectors are seen as most useful in alleged sex offences for which there are usually no independent witnesses.

A solicitor and barrister who recently put a client accused of a sex offence through a polygraph test and sent the results to police has called for them to be available nationally to aid investigations and prevent miscarriages of justice.

Mike Gibbons, a solicitor of Litigaid Law in Southport, who was formerly a police detective in London and Merseyside, and Mark Tomassi, a barrister, said: "My client said the sex had been consensual. He passed a lie detector test with flying colours. In the end he was never charged.

"… A person suspected of sexual crime could and should be offered the opportunity to take a lie detector test … If such a test is sufficiently reliable to protect the public from future offences from those already found by the courts to be guilty, it is but a modest proposal to allow an innocent person at least a chance of persuading a prosecutor to think again."

The use of lie detectors are also popular outside of the field of police investigations. Bruce Burgess, a founder member of the British Polygraphic Association who runs UK Lie Tests, says that suspected infidelity is the most common reason for private customers requesting the tests, which cost £600 or more.

"Generally it's to find out whether wives or husbands have been cheating," he explained. "Sometimes it's a text message that has gone the wrong way, or something on Facebook [that triggered suspicion]. "You can ask three questions on one issue. If anyone one fails on one question they fail on it all. It's pass or fail. I stay with them after the test. A lot of them shout at each other." Burgess's firm has even carried out tests for ITV's Jeremy Kyle show where couples have accused each other of infidelity.

Burgess is also frequently asked to test people in relation to allegations of sex abuse. "Sometimes we test victims, sometimes perpetrators. Sometimes it's gone to court. I have given statements to police when people have made admissions after a test.

"I don't think it will be used [as evidence] in courts. Even in the United States it's hard to get it in to court. Prosecution, judge and defence all have to agree to accept it. But I think the police should use it as an investigative tool as the they do in the US. It can help police home in on a suspect."

Commenting on the spread of polygraphs, justice minister, Andrew Selous said: "This government is introducing lie detector tests for high risk sexual offenders, as well as satellite tagging to track their movements. We are determined that the UK has one of the toughest regimes in the world for managing sex offenders, to stop reoffending and to protect victims."