Norfolk Constabulary has announced plans to stop attending emergency calls related to mental health incidents.
Under the changes, officers will only attend such calls where a crime has been committed or there is an immediate threat to life.
The new policy - which will come into force by the end of the year - is intended to free up police resources to tackle crime. Currently one in every five calls the force receives are related to mental health.
However, the change is likely to prove extremely controversial, with concerns that it could leave vulnerable people at greater risk.
And it may increase pressure on the NHS and other bodies, as they fill roles no longer filled by police.
When the Metropolitan Police announced similar plans last week, they were heavily criticised.
Zoe Billingham, chairman of the Norfolk and Suffolk NHS Foundation Trust, led national opposition to those proposals, saying they would create a "vacuum".
Norfolk Constabulary's plans involve following an initiative piloted in Humberside called 'Right Care, Right Person'.
This involves more carefully screening 999 calls to determine whether or not officers should attend.
It would raise the threshold for which calls they are sent on, depending on whether anybody's life is at immediate risk.
The policy follows growing frustration among officers at what they see as the time they spend picking up the slack for over-stretched NHS resources.
An increasing amount of police time is spent accompanying people waiting for mental health assessments or conveying people to hospitals due to ambulance shortages.
Officers also say they are not necessarily the most appropriate people to respond.
Deputy chief constable Simon Megicks said: "All too often, police officers are dealing with situations that could be handled by other, more appropriate agencies.
"This includes people in mental health crisis, who need the help and support of professionals and not the skills of police.
"This type of demand is ever-increasing with one in five calls we receive mental health related.
"We are therefore letting our communities down twice; firstly, by not sending the right resource to people suffering mental ill-health and secondly, spending a large amount of time away from the core business of preventing and solving crime and supporting victims.
"The Right Care, Right Person initiative is about giving people the right support when they need it, from the right agency."
Mr Megicks insisted the policy would not see the force completely stop attending mental health-related calls.
He added: "We would never make a decision that would put people in danger, and we will continue to attend incidents where a crime has happened, or where there's harm or a risk to life.
"Policing will always have a role with people suffering mental ill-health, but we can not bridge the gap in service provision of other agencies.
"This is not a sustainable position or one which is good for patients.
"Being dealt with by the police can have a detrimental impact on vulnerable people."
Ms Billingham said: "I am pleased that in Suffolk and Norfolk there will be no unilateral withdrawal of police from mental health crisis calls.
"The work of the NHS and police has, and always will be, a partnership.
"At the heart of all we both do and stand for is protecting our most vulnerable people.
"We will continue to work together to adopt Right Care, Right Person to ensure people in Norfolk and Suffolk who are experiencing a mental health crisis get the care they need."
The Right Care, Right Person initiative was first introduced by Humberside Police three years ago, after the force identified a number of circumstances in which officer time was being consumed by mental health-related tasks.
Mr Megick added that the constabulary would be taking a "phased approach" to bringing in the initiative, working alongside partners in health organisations.
The constabulary's approach has been backed by Pete Boczko, chief executive of mental health charity Norfolk and Waveney Mind.
He said: "Norfolk police are very good at asking us and other partners what would work best.
"As a system, the NHS, the voluntary sector and the police have got to work together to limit the types of situations where officers have to get involved.
"Police officers are not specifically trained to deal with mental health - so how have we got to the point where they are among the first point of call?"
ANALYSIS: A CHANGE FRAUGHT WITH RISK
The issue of police involvement in mental health care is one that has been hotly-debated since the Metropolitan Police announced its intentions to stop responding to this type of call.
Now Norfolk Constabulary has confirmed it is planning to follow suit.
Like most debates involving mental health, this is an incredibly delicate topic.
To a large extent, responding to such cases is not, nor has it ever been, the core role of the police.
However, it is a core role of the police to ensure lives are kept safe.
This is why, if the police are to scale back their involvement, it has to be done in an extremely careful way.
Mental ill-health can be an extremely volatile thing and as a consequence, situations can escalate themselves very rapidly and with little warning.
If the threshold for officers to attend is raised too drastically, then there may very well be dire consequences resulting in a person, or people coming into harm.
The other question that needs to be answered, is if the police do not attend, then who will?
It is clear the NHS is struggling to cope with the demand for mental health care that it is facing.
The emergency services working in partnership with one another is nothing new and has always been a big part of the police's role in society.
While the prospect of officers having more time to investigate crime is welcome, work needs to be done to ensure freeing them up is done in a safe and sensible way.
A big part of the current issue is that officers are not adequately trained in looking after people with acute mental health problems.
Perhaps then, this is something that needs to be addressed as well.
We all want to see our men and women in blue doing what they do best - fighting crime and protecting us - but this step back will only prove counterproductive if it puts lives at risk.
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