Spending on bonuses and other performance pay for top federal government executives increased by more than double the rate of inflation in Prime Minister Justin Trudeau's first year in office, CBC News has learned.

The 3.2 per cent increase in spending for 2015-16, the most recent year available, was also more than twice the 1.25 per cent pay increases the government has negotiated with many of its public sector unions.

Spending on performance pay for top executives increased to $75 million from $72.6 million the year before with wide fluctuations in the percentage increases — or decreases — in many departments.

Spending on performance pay for deputy ministers increased 3.4 per cent to $4.7 million.

The head of Canada's largest public service union questions why spending on performance pay increased by more than the salary increases for public service workers.

"We hope the government isn't handing out an increase to their executives that is out of step with the wage increase it was willing to give our hard-working members. It's the responsibility of the government to explain this increase in executive performance pay spending," said Robyn Benson, national president of the Public Service Alliance of Canada.

Like many corporations, the federal government offers a system of performance pay designed to attract the best and the brightest into the public service.

Robyn Benson, president of the Public Service Alliance of Canada, is calling on the government to explain why spending on executive performance pay outpaced public service salary increases. (CBC)

Those who perform to the level expected get "at-risk" pay, a term that reflects the fact that executives and deputy ministers risk not receiving it if their performance is not satisfactory. Bonuses on top of the maximum at-risk pay go to those who perform above and beyond expectations.

When it comes to doling out performance pay, executives and deputy ministers are evaluated on how successful they have been in running their own departments and in implementing objectives set by the government.

In 2014-15, for example, the objective was successfully implementing the Harper government's cost-cutting plan. The more jobs and costs top executives cut, the more performance pay they got.

In 2015-16 the priority centred on recruiting people with skills needed in the future and improving mental health in the workplace.

Currently, in addition to promoting a healthy workplace, the Trudeau government has made it a priority to increase the social and cultural diversity of the public service and to support efforts to fix the problem-plagued Phoenix pay system.

The numbers are not detailed enough to know, however, whether those at Public Services and Procurement who were responsible for Phoenix received performance pay.

Basic salary ranges for those in the federal government's EX category in 2015 range between $106,900 and $202,500 a year.

Deputy ministers' paycheques that year ran from $192,600 a year to $326,500.

But for those who are judged to be good at their jobs, their base salary was just the start of what they took home in 2015-16.

The biggest increases in performance pay were at Immigration, Refugees and Citizenship Canada (IRCC) and the Canadian Human Rights Commission (CHRC). The number of executives at the latter rose to 15 from 11, and overall spending on executive performance pay was up 22 per cent.

The Public Prosecution Service of Canada was up 17 per cent overall, in part because adding the Commissioner of Elections office created an additional executive position. Two executives also received bonuses that year, compared with none in 2014-15.

At the Canada School of Public Service, the Canadian Environmental Assessment Agency and the Department of National Defence, performance pay was up 14 per cent.

Daniel Lebouthillier, spokesman for National Defence, said the number of executives eligible for performance pay rose in 2015-16 to 190 from 172.

At the other end of the spectrum, executive performance pay spending at the Civilian Review and Complaints Commission for the Royal Canadian Mounted Police dropped 28 per cent, followed closely by the Canadian Northern Economic Development Agency (CanNor) at 27 per cent.

Performance pay spending at the Office of the Commissioner of Official Languages dropped 20 per cent, and dropped 17 per cent at the Public Health Agency of Canada.

Several departments and agencies said the fluctuation in spending on performance pay was the result of an increase or decrease in the number of executives eligible for performance pay. In organizations with fewer executives, small staffing changes sometimes led to double digit percentage changes.

At the immigration department, the increased performance pay was to "recognize the outstanding contribution of the department's executives on the Syrian refugee resettlement file and other significant operational initiatives," said spokesperson Lindsay Wemp.

For those who get performance pay, it can translate to thousands of dollars a year.

Treasury Board president Scott Brison's office says it is up to deputy ministers and the clerk of the privy council to decide how performance pay is doled out. (Sean Kilpatrick/Canadian Press )

The Transportation Safety Board had the highest average at-risk pay that year — $18,008 — followed by the Finance department, where executives got an average of $16,530. Executives in the Privy Council Office, which co-ordinates the government's actions and supports the Prime Minister's Office, got an average of $15,866 in at-risk pay while those in the Department of Western Economic Diversification got $15, 440 and Infrastructure Canada executives got $15,399.

The lowest rate for at-risk pay was at the Canadian Northern Economic Development Agency where executives received $9,565 on average, followed by the Public Prosecution Service where executives got an average of $10,937 and the Parole Board at $11,088.

The highest average bonuses — $10,836 — went to executives in the department of Western Economic Diversification, the Immigration and Refugee Board and the Public Service Commission, which oversees hiring and appointments of federal government employees.

Privy Council executives got average bonuses of $7,809 while bonuses for Finance department executives averaged $6,749.

Nine of 56 departments and agencies for which figures were available paid out no bonuses.

Treasury Board president Scott Brison's office declined to comment on the increased spending on performance pay, saying the decision is "the prerogative" of the Clerk of the Privy Council and deputy ministers.

Treasury Board officials said a variety of factors contributed to the increase, including a higher average amount of performance pay per executive, a greater number of executives who received performance pay and the impact of wage adjustments.

Elizabeth Thompson can be reached at elizabeth.thompson@cbc.ca