The Greens say they would grow the federal public service by 15,000 and pay them 4 per cent more a year.

The party released its public sector policy this week (PDF), which would scrap the Coalition's cap on government staffing and replace it with a cap on consultants and contractors.

Greens leader Richard Di Natale said the party wants to enshrine public servants' right to express political views in law.

Dr Di Natale said the Australian Public Service had been “privatised by stealth” since Tony Abbott's era.

“Job cuts by successive governments have hollowed out government departments, creating a stronger reliance on the big four consulting firms, all of which are big donors to the major parties,” he said.

The Greens say they will push whoever wins the upcoming election to reverse recent job cuts and restore staffing to 2012-13 levels - creating an extra 14,500 full-time-equivalent jobs.

It comes after the Coalition government shed 12,000 public service jobs, which the Greens say has led to “out-of-control” public spending on labour-hire and consultants.

The party says it will “put an end to the gravy train for consultants and contractors and put an end to the 'brain drain' from the public service to private companies”.

Capping spending on consultants and contractors at 7.5 per cent of each agency's budget is predicted to save about $10.2 billion over a decade.

Additionally, departments would be banned from using labour-hire companies, “except in exceptional circumstances, and unless approved by the minister and reported to parliament”.

Labor also says it would remove the cap on public service staffing, but has not explicitly recommended increasing the bureaucracy's workforce.