UK police forces dealt with nearly 300,000 incidents involving people with mental health problems last year, figures reveal.
Campaigners said the "shocking" figures revealed a lack of funding and provision for those with mental health problems and called for further investment to help people before they reached a point where they were in contact with police.
They also called for police to have better support in dealing with people in a mental health crisis.
The data obtained under the Freedom of Information Act showed 296,773 incidents were recorded in 2016.
South Wales Police having the highest number of any force at 38,712.
This was followed by Nottinghamshire Police, which registered 19,973 incidents with a mental health code, and the Police Service of Northern Ireland, which registered 19,668.
Danny Bowman, mental health spokesman for think tank Parliament Street, said: "These findings reveal the shocking numbers of mental health issues currently being dealt with by police forces across the country.
"It's time to recognise that Britain needs a better funded strategic plan to ensure people who are suffering with mental health problems are properly cared for by specialist health services."
Paul Farmer, chief executive of the mental health charity Mind, said: "Mental health is core police business.
"Getting people the right help as early as possible means people can manage their mental health, are less likely to end up in crisis and, ultimately, will reduce pressure on all emergency services."
A Government spokesman said: "People experiencing mental health crisis need the right care in the right place, not a police cell.
"We're investing £30 million in providing more alternative places of safety, have more than halved the number of people detained under a mental health section in a police cell in the last year and are entirely banning the use of police stations for this purpose for under 18s."