Police Scotland insist "there is no overtime ban"
Police Scotland have said "there is no overtime ban", after claims officers were told to abandon drug investigations in case they had to work extra hours.
The rank-and-file whistle-blower said he risked "career suicide" by revealing his concerns.
The general secretary of the Scottish Police Federation (SPF), Calum Steele, published an email from him on twitter.
Police Scotland said there was no specific cap on overtime spending.
Calum Steele said the "sensational" claim was just "the tip of a very large iceberg".
The email states: "Officers... are on an overtime ban.
"Whistle-blowing on anything like this is career suicide... so I'd rather my identity not be published.
"We are being told not to be proactive and investigate drug dealers because (they) could cause overtime, but rather just do the work we are given."
Another email states "people who should be held (in) custody are being released, on undertaking to avoid officers staying on to complete (a) case and incur overtime".
The force is facing a £21m shortfall in running costs this year, dwarfing the £18m overspend last year, despite an £18m budget boost from the Scottish government for 2016/17.
The number of drug-related deaths has jumped by 15% in a year to the highest figure ever recorded, official figures released on Wednesday show.
Mr Steele told BBC Scotland: "They're being told if they do incur overtime, they won't be getting paid for it.
"Now whether you call that an overtime ban, or a strict examination of the overtime budget it ultimately makes no difference, because if there is no overtime available to pursue those that are engaged in activities like drug dealing, then ultimately the public suffer."
He said the Scottish government must now "put its hand in its pocket" to protect the public.
A Police Scotland spokesman said: "There is no overtime ban in operation. Officers across Scotland continue to focus on meeting local priorities, including tackling drug dealers in communities, drug supply at local, national and international level and reducing the harm caused by drug abuse."
A Scottish government spokeswoman said: "We will do everything to tackle the scourge of illegal drugs, by applying the full force of the law to hitting dealers who peddle misery that blights the lives of so many, while supporting those living with an addiction.
"We are committed to protecting the police revenue budget in real terms for the entirety of this parliament, delivering an additional £100m of investment over the next five years, in addition to £55m of reform funding in 2016-17.
"Clearly, it is for SPA and Police Scotland to determine the best possible use of the budget according to national and local priorities."
In an interview with BBC Scotland, Aileen Campbell MSP said: "Police Scotland is a crucial partner in our approach to tackling drug misuse across the country.
"They're a really incredibly positive partner in our approach to tackling some of the issues that we have in our country and I know they are taking forward some really innovative work across the country as well, and are dedicated to keeping our country safe."