West Yorkshire police officers face random drug and alcohol testing when the force brings in a tough new policy on substance misuse later this month.

From November 20 many officers - including all those on "safety critical" traffic and firearms duties - can expect to be routinely checked.

New recruits and officers in their probationary period also face random tests as does any officer suspected of being unfit for duty because of drug or alcohol misuse. And the rigorous new breath test sets a much higher standard than the country's drink-driving laws.

Officers with drug or alcohol problems are being strongly urged to seek help before testing begins.

The force has assured those who come forward that they will be given "the maximum support and assistance".

A spokesman said: "If an officer self-declares and undergoes rehabilitation before being tested they may not be subjected to misconduct proceedings."

Tom McGhie, chairman of the West Yorkshire Police Federation, said his members supported the new policy.

He said: "We cannot condone the misuse of illegal substances.

"People with substance-misuse problems put themselves at risk, their colleagues and members of the public.

"We have been consulted about the introduction of these policies. The West Yorkshire force has not rushed into this and we believe it won't be fully implemented until April."

He said the policy was ratified in September and since then all officers had been made aware of the impact it could have on them.

Mr McGhie said: "We don't think there is a widespread problem. Most police officers are responsible in their behaviour and come to work fit for duty, but you can never say never."

Mr McGhie said he had spoken to Federation members in North Wales, where the policy was already in place, and no officer had so far tested positive.

Superintendent Trevor Kerry, of West Yorkshire Police Professional Standards Unit, said: "The introduction of this policy is essentially about safeguarding and maintaining the welfare of all our officers.

"It also ensures that the force maintains high ethical standards in order to maintain public confidence."

Tests, other than for recruits, will be urine samples taken by an independent collection agent.

Officers caught reporting for duty with more than 13 microgrammes of alcohol in 100 millilitres of breath (the legal limit for driving is 35) will be considered unfit for duty and may face misconduct proceedings. The new policy was drawn up in November last year by the Home Office e-mail: newsdesk@bradford.newsquest.co.uk