Mrs Mulligan said: "A lot of work has been undertaken by North Yorkshire Police to understand the demand placed on officers by people in mental health distress, and it is frustrating we can not yet pinpoint it accurately".
That is placing an intolerable burden on police officers and staff, resulting in a national crisis which should not be allowed to continue.
"We are seeing forces attending less other crimes because they are focusing on mental health-related incidents", said HM Inspector Zoe Billingham, who led the investigation.
She added: "All too often, the system is failing people when they most need help".
It comes after West Yorkshire Police chiefs warned that they were facing increasing calls on their time despite dwindling resources. And we found that police officers respond to those with mental health problems with care and compassion.
Police involvement could include responding to emergency contacts from concerned relatives or friends, making welfare checks at the request of social services or Global Positioning System, supporting victims of crime who have mental health problems, attending incidents where someone is suicidal or searching for missing people.
"We also focus on continued training for our officers, staff and call handlers resulting in them being able to identify people who may have mental health issues and ensure we are offering appropriate support".
"We have grave concerns about whether the police should be involved in responding to mental health problems to the degree they are". It cost the force an estimated £70,000 just to answer the calls.
The chancellor of the exchequer unveiled plans for a new NHS mental health crisis service in the Autumn budget this year, which is set to include mental health support in every major A&E department, more mental health ambulances, "safe havens" in communities and a 24-hour mental health crisis hotline.
"We are police officers, not social workers or medical experts". This is not a problem that the police alone can solve. "Miss Billingham said other services 'need to stop relying on the 24/7 availability of the police".
"Fundamental change is needed urgently in the way those with mental health problems are supported by the state".