Ontario will no longer allow the Canada Border Services Agency to join the province's road safety blitzes, which in the past have been used by federal agents to make arrests on immigration violations, the government announced Friday.

Transportation Minister Steven Del Duca sent a letter to federal Public Safety Minister Steven Blaney saying that partnering with the CBSA "does not align" with his ministry's mandate to make roads as safe as possible.

Ontario's Liberal government ordered the review after a joint commercial vehicle roadside blitz in Toronto in mid-August led to the arrest of 21 undocumented workers.

"As a result, effective immediately, the ministry will no longer partner with the CBSA on commercial motor vehicle enforcement initiatives," wrote Del Duca.

"The ministry will only partner on joint enforcement initiatives with road safety partners that have a shared objective to protect and ensure road safety and commercial carrier compliance."

Ont New Cabinet 20140624

Ontario Transportation Minister Steven Del Duca says a partnership with the federal border services agency is not consistent with his ministry's mandate. (The Canadian Press)

The arrests at the Toronto blitz of commercial vehicles were the catalyst for reviewing the province's relationship with the border agency, said Del Duca.

"It was that initial incident that caused me to ask questions and ask for the review," Del Duca said in an interview.

21 arrests during blitz

Blaney's office defended the practice of arresting people for immigration violations during road safety blitzes.

"Minister Blaney is concerned about this decision and will respond to Minister Del Duca's letter," said spokesman Jason Tamming.

"As a result of this blitz, CBSA was able to apprehend over 20 people who were violating Canadian laws."

Del Duca insisted that partnering with the CBSA wasn't in line with his ministry's objectives.

"This is not to suggest CBSA does a good job or a bad job," he said.

"It became pretty clear to me that partnering with CBSA didn't necessarily make sense with respect to being in alignment with our road user safety goals and objectives, and that's why we made the decision to end the relationship."

NDP wrote ombudsman

Ontario's New Democrats wrote Premier Kathleen Wynne after the arrests to say that the roadside inspections are meant to improve safety and are "not for immigration-related interrogations, arrests and deportation."

NDP immigration critic Teresa Armstrong also wrote Ombudsman Andre Marin last month asking him to launch a formal investigation into the joint operations between the Ontario Ministry of Transportation and the CBSA.

"I feel the ministry investigating itself is insufficient," wrote Armstrong of the internal review ordered by Del Duca. "This investigation merits a review by an independent body."

Del Duca's letter to the federal government said Ontario will keep inspecting commercial vehicles at border entry points because "they do not involve CBSA resources."

The transportation minister said the province has an excellent road safety record in part because of the vigilant roadside spot checks of vehicles.

"We can always do better, but we've delivered some pretty great results," he said.