The government has announced plans to slash public service jobs by about 14 percent over the next three years in a shake-up it says will deliver $2.4 billion of savings.

The changes announced in a pre-Budget speech delivered by Finance Minister Nicola Willis on Tuesday would result in about 8700 job losses by mid-2029.

"Historically, core public service numbers have been equivalent to about 1 percent of the population. After a period of largesse under the last government it now hovers around 1.2 percent.

"We will be tracking progress towards a numerical target of no more than 55,000 full-time equivalent public service employees by July 2029. That's 8700 fewer than were employed in December last year," Willis said.

Read more: How many public service jobs may have been axed already, and from where