Hertfordshire’s Police and Crime Commissioner has called on members of the public to intervene when they witness crimes taking place.

David Lloyd spoke of a 50 per cent decline in public intervention in crimes over the last decade which "leaves our society at risk".

Speaking at his first annual lecture at the University of Hertfordshire on Monday (April 15) evening, the Police and Crime Commissioner spoke of an incident in the north of the county in which members of the public cheered on a group of youths as they assaulted police officers outside a nightclub.

He said: "The decline in public intervention leaves our society at risk.

"Evidence shows that citizen’s arrests have declined by half over the past ten years.

"This is fuelled by fear of the consequences not simply from the criminal’s reaction but a lack of certainty that the police will support these actions.

"I am not saying that everyone should intervene in every instance.

"People should have regard for their own safety and should not put themselves into positions of high risk but I fear that too many of us have reverted to a default response of not intervening, thinking that it is only the job of the police.

"Even worse, there is a tendency to turn a blind eye and not even bother to report things to the police."

Quoting from Nine Principles of Policing by Robert Peel, the founder of the Metropolitan Police, Mr Lloyd said: "Police must secure the willing co‐operation of the public in voluntary observance of the law to be able to secure and maintain the respect of the public."

The PCC, who was elected to the post last November, added that cases like Gary Newlove, a 47-year-old man who was beaten to death after confronting a gang of youths who were vandalising his car, should not deter people from intervening.

He said: "How should we respond to incidents of this type?

"Is this a justification for us never to intervene in any situation for fear that the same fate may befall us? I would argue no."

He added that too often the criminal justice system "favours the offender and not the victim".

He continued: "There should be a presumption that the rights of the intruder are reduced once they enter someone’s property or are committing any criminal act.

"This is not a call for vigilantism but just that someone who takes the premeditated step to burgle someone’s house or steal someone’s car needs to accept that the owner can rightly take steps to protect their property and to protect themselves and their family.

"So the police interpretation should be on the side of the victim not the intruder.

"The wider criminal justice system should also operate this presumption."

In 2009, Roland Digby from Royston was charged with assault by Hertfordshire police after making a citizen's arrest on a youth he claimed was throwing crab apples at his house. He appeared in Stevenage Magistrates' Court before the force dropped the charges against him.