Police Scotland says it will cut civilian staff jobs and freeze recruitment in order to save money and maintain officer numbers.
The force said that “hard choices” had to be made to deliver policing with its current Scottish government budget.
Unison said it had not been consulted and did not agree with the move.
Police Scotland said the recruitment pause – which began on Wednesday – would not apply to priority areas such as contact centres or custody.
Officers numbers would remain at around 16,600, with support staff numbers to be reduced “proportionately”.
A Police Scotland spokesperson said: “The revenue budget does not allow us to maintain our workforce at the levels of previous years and at the same time make a fair pay award.
“Hard choices are being taken to deliver effective policing within the funding available.
“Urgent action is being taken to achieve savings, with areas which encounter the greatest demand and which carry the greatest risk in keeping people safe being prioritised for resources.”
The force previously warned of financial pressures threatening the service, with officer numbers at their lowest number in Scotland since 2008.
Former Chief Constable Sir Iain Livingstone also said it would have to be “even leaner” in its delivery of key services to deal with budget pressures.
Staff union, Unison, said it would mean “more work for already stressed staff”.
Regional organiser Deborah Clarke said: “This decision by Police Scotland is an imposition on police support staff, who are already working flat out.
“Unison has not agreed to a recruitment freeze and Police Scotland have not consulted us.
“It’s another top down decision taken with no consideration as to how it will affect hard-working police staff.”
The Scottish government said Police Scotland was a “vital service” and funding had been increased in difficult financial circumstances.
A spokesperson said: “We have increased police funding year-on-year since 2016-17, investing more than £11.6bn since the creation of Police Scotland in 2013.”