People who go missing in Avon and Somerset and are deemed "low-risk" may not spark a police search for 36 hours.
The change in policy comes as the force declares itself at tipping point after years of budget cuts and falling officer numbers.
Avon and Somerset Police says up to 30% of its daily resources are being spent looking for "high-risk" missing people rather than solving crimes.
A charity warned that the approach could endanger vulnerable children.
As numbers are rising, the force is now considering who to actively search for, as 40% of those who go missing disappear more than once.
What is low risk?
According to official police guidelines:
- A no-risk missing person (not used for children in Avon & Somerset) is where no there is no risk of harm to either the subject or the public
- A low-risk missing person is where risk of harm is assessed as possible but minimal - for instance an adult who has had a family argument and storms off but has no history of self-harm/mental health issues
- A medium-risk missing person is where risk of harm is "likely but not serious", possibly a child who repeatedly goes missing or somebody with dementia who goes missing a lot
- A high-risk missing person is where harm to them or the public is very likely
The force spends between £24,000 and £40,000 every day on missing people, but said it would not change when it hunted for those deemed at high-risk.
Det Supt Richard Kelvey said: "We are at a point where we have to say to some families, 'call us in 12 hours' time'.
"If we didn't deal with missing people, we would probably have 300 more people on the ground."
- In 2017-2018 the force was alerted to about 8,000 missing people - about 26 a day
- Forty per cent of those who go missing are children
- About 4,500 people go missing more than once - for some it is 50 times in a year
- Seventy-five per cent of missing people are found within 24 hours, and many return of their own accord
- Many are adults in crisis or vulnerable children in care
The police force said when delaying the deployment of officers for low-risk cases, they reassured relatives and advised them to call back in 12 hours if they felt "the risk had changed".
The charity Missing People UK says it has concerns as seven out of 10 children who were sexually exploited were reported as missing.
Karen Robinson, from the organisation, said: "With Operation Bullfinch in Oxford, many of the girls who were exploited had had repeated missing episodes, but were mistakenly deemed as 'low-risk'.
"Focussed, well-resourced policing teams to assess and respond to these risks are vital, because when someone goes missing it is a sign that something is very wrong."
Avon and Somerset Police has said it is "highly unlikely" its officers would deem a child as low-risk. If the young person was particularly vulnerable, such as being in care, they would be prioritised.
But Mr Kelvey said despite the delayed approach, teams still used 30% of their time on missing people daily.
"The people that unfortunately kill themselves are normally dead by the time we are told about this - it's very sad but true," he said.
Avon and Somerset Police Federation said the force had 700 fewer officers, and it blamed government cuts.
The Home Office has pledged an extra £161m this year for England and Wales' 43 police forces, which its says will protect police budgets in "real terms".