EDMONTON - Saskatchewan Premier Brad Wall renewed his attack Wednesday on Justin Trudeau's employment insurance changes but the prime minister said the issue boils down to "cold, hard mathematics."

Wall praised the extensions to EI coverage for 12 areas hit hard by the resource downturn, but questioned why the government employed a straight-up regional statistical cutoff rather than helping people in specific industries, such as oil and gas.

"It's not a lot, but it's certainly a step in the right direction, except the federal government excluded two-thirds of our oilpatch," said Wall.

Wall took aim at some of Trudeau's comments from Tuesday, when the prime minister said those in Edmonton and Saskatchewan complaining about being left out of changes should feel fortunate their areas have not been harder hit by the downturn in energy prices.

"I know those laid-off workers," said Wall.

"If the federal government has a program to help provide a bit of support for energy workers, why in the world would they exclude southwestern Saskatchewan, southeastern Saskatchewan, and why then would anyone say that you should happy about that? They're not happy about that."

Last week's federal budget included provisions to help workers in regions where the unemployment rate increased by two percentage points or more for a sustained period over the last 12 months when compared with the lowest point between 2014 and early 2015.

The 12 regions are: Whitehorse, Nunavut, northern British Columbia, northern Manitoba, northern Ontario, Newfoundland and Labrador, northern Alberta, southern Alberta, northern Saskatchewan, Calgary, Saskatoon, and Sudbury, Ont.

The budget adds five weeks to the regular 45 weeks of EI benefits, effective in July and retroactive to January 2015.

Long-tenured workers will also be eligible for an extra 20 weeks of benefits, to a maximum of 70 weeks.

Alberta Premier Rachel Notley has expressed concern that workers in Edmonton have been excluded.

The job losses have been less severe in the Alberta capital due, in part, to the city being home to many provincial civil servants.

Notley's government has not cut the civil service during the downturn, saying that would make a bad situation worse.

Trudeau faced renewed questions on the Edmonton exemption while touring the city Wednesday.

He reiterated that the federal government is not arbitrarily picking winners and losers.

"We're applying the cold, hard mathematics," Trudeau told reporters after meeting with families at a southside library.

"We're continuing to base our decisions on evidence and facts and making sure that we're helping out the people who need the help the most."

- With files from Jennifer Graham in Regina