Once that choice was made, she said, the Harper government put so much emphasis on saving money that it undermined efforts to ensure that the system would function well.

“When they say IBM is adhering to the terms of the contract, it’s true,” Ms. Daviau said. “The government just didn’t scope out the contract properly.”

At a parliamentary committee hearing in September, Ms. Foote said the Conservatives had skimped on training for the 500 workers hired to run Phoenix, “versus actually buying into what IBM had advocated as the amount of training that really needed to take place.”

While the Conservatives have avoided answering direct questions about their role in the system, they have repeatedly accused the Liberal government of bungling what they started.

“Blaming the previous government is like taking home a nice steak from the butcher and then burning it and blaming the butcher,” Kelly McCauley, the member of Parliament who is the Conservative spokesman on the issue, said at the September hearing.

The potential for trouble was apparent early on. In May 2015, when the Conservatives still held power, IBM recommended pushing back the planned start-up of Phoenix at the end of that year. It was postponed until February, but the government went ahead with layoffs of the payroll clerks anyway, making it impossible to keep the old system operating as a backup in case of teething trouble with Phoenix.

Phoenix’s problems are far from being untangled, and new issues keep appearing. But the government has managed to reduce the number of employees who have pay problems to about 18,000, in part by rehiring some of the laid-off payroll clerks to help out. After a fitful start, an emergency pay system appears to have ended the need for managers to dip into their own bank accounts to help employees.