OTTAWA - - A federal budget billed as promoting jobs and growth will put some 19,200 public servants out of work.

An estimated 12,000 jobs are being cut, while the remaining positions will be eliminated through attrition.

Public servants could begin learning their fate by Friday as departments begin to implement the cuts mandated by Thursday's budget.

"The services these people provide are going to be affected," warned John Gordon, president of the Public Service Alliance of Canada.

The job losses in the public sector are far lower than some of the worst-case scenarios proposed by advocacy groups, some of which predicted as many as 60,000 jobs could be at risk as the government sought to slash program spending.

"It is expected that the proposed reduction in employment, which represents only 0.1 per cent of all jobs in Canada, will be marginal compared to the expected job growth in the wide economy over the course of the three years in which the reductions will be implemented," budget documents state.

The estimated cost of the layoffs is $900 million.

A large proportion of the cuts will be in the Ottawa-area; regional positions will be mostly untouched.

The government says the cuts reverse only about 20 per cent of the increase in federal jobs that's occurred since the late 1990s.

Statistics Canada says there were about 400,000 people working for the government in 2011, which includes military personnel.

The job cuts are the result of a government-wide spending review that's resulted in a 6.9 per cent reduction in program spending, though hundreds of government workers have already been laid off over the last year after previous expenditure reviews.

A coalition of six public-service unions representing more than 75,000 government professionals said the cuts are putting the public at risk.

"This budget continues with the drastic reduction of the public service to meet the bottom line, but at what cost? We are very concerned that programs critical to the safety and security of Canadians are impacted," said Gary Corbett, president of the Professional Institute of the Public Service of Canada, on behalf of the coalition.

The budget document does not set out precisely where all the layoffs will be felt, but offers a few clues.

Some government programs are being eliminated, while several departments with overlapping mandates are merging their office functions.

"These are the types of things we need answers to," Gordon said.

"You can't just stand up in Parliament and say we're cutting this and cutting that without telling Canadians and telling parliamentarians, here's how we're going to do this."

The new cuts will be rolled out over time as collective agreements between the government and unions contain workforce adjustment measures that could see some affected employees moved into vacant jobs.

Public sector employees will also see their pensions change.

Currently, employees pay 40 per cent of the contribution to their pension but the government is proposing to increase that to 50 per cent.

They're also changing the retirement age from 60 to 65 for people who join the civil service after 2013.

Gordon said that will pose a recruitment problem for the government in the long-term.

"When someone is coming into any job, one of the things they look at is a career, what's my compensation, what's my benefit package going to be?" he said.

"If they are taking things away from it, people are going to say that's not the place for me to go."