Britain's Justice Secretary has defended plans to make terrorists take a lie detector test to prove they have reformed and are not planning to carry out another attack.

Plans to introduce "polygraph testing" were announced by the British government as part of a wave of measures being described as a "major overhaul" in the way terrorists are punished and monitored.

The measures, which include tougher sentences to see terrorists locked up for longer, come in the wake of the London Bridge attack.

When questions were raised over their accuracy, Robert Buckland insisted lie detectors were important to identify "sleepers" and that they will not be the only measure used.

He told Sky News: "You can get people who are in effect sleepers for many years and then suddenly back come the hatreds and the prejudices and we see atrocities like the one we did at Fishmongers' Hall."

Pressed on accuracy of the tests being as low as 60%, Mr Buckland said: "I'm not pretending on their own, polygraphs, lie detectors, are the be-all-and-end-all, which is why what we are also doing is doubling the number of specialised counter-terrorism probation officers... improving training, getting more psychologists in there, specialist imams as well will be working with these people."

Meanwhile he told BBC Breakfast the proposal was "not a new concept", with detectors introduced about seven years ago to assess the risk posed to the public by sex offenders.

He insisted it was a "sensible measure in order to help maximise the understanding of the risks that some of these prisoners pose to society" which would not form part of a criminal investigation or evidence used in court.

Some experts have questioned the credibility of polygraph tests, claiming there are ways of cheating to manipulate the results.

Professor Aldert Vrij, a senior lecturer in psychology at the University of Portsmouth who has written extensively on the subject, told the BBC in 2018: "It does not measure deception, which is the core problem."

Others have suggested because taking the test is a stressful experience this could provide the wrong results by indicating an innocent person is lying.

The FBI reportedly asks new staff to submit to a test when they join but according to the American Psychological Association "there is little evidence that polygraph tests can accurately detect lies".

More details of The Counter Terrorism (Sentencing and Release) Bill were released less than two months after convicted terrorist Usman Khan embarked on a killing spree armed with two knives and wearing a fake suicide vest after attending a prisoner rehabilitation programme while out on licence halfway through a 16-year jail sentence.

Saskia Jones and Jack Merritt were both killed and Khan was shot dead by police.

Shadow home secretary Diane Abbott described the announcement of a security overhaul as "an admission of failure" by the Government.

Liberal Democrat home affairs spokeswoman Christine Jardine said judges already had the power to lock up terrorists for life while polygraphs were "not accurate or reliable enough" for such critical decisions.

In the year to the end of September, there were 44 convictions for terrorism offences, with 17 offenders being sent to jail for between four and 10 years, the government said.

Five were jailed for ten years or more and one was handed a life sentence.

Around 245 convicted terrorists were freed from jail between 2012 and 2019.