The Conservative government's proposed changes to who can qualify for welfare amount to an effort to pressure provinces into adopting anti-refugee policies, say critics who are picking a new fight over benefits for refugee claimants.

Nearly 160 groups from across the religious and social spectrum are calling on the government to reverse measures, buried in the latest omnibus budget bill, which open the door to refugee claimants being denied welfare.

The Conservatives say they are just giving provinces the flexibility to determine benefits, but it's not a benign change, Michele Biss of the group Canada Without Poverty told a news conference Tuesday.

"The federal government is offering a financial incentive as a means of the provinces implementing the government's ideological driven policies towards refugees," Biss said.

Currently, if provinces place any residency restrictions on who is eligible to receive social assistance, they could lose some of the money they receive from the federal government to cover those services.

The blanket prohibition against restrictions is meant to ensure a national standard for access to social services, so that everyone receives the same level of support no matter who they are or where they live.

The budget bill seeks to change that, creating categories of people to whom residency requirements cannot apply.

For example, the proposed legislation wouldn't cut off benefits to people whose refugee claims have been approved or who are already permanent residents or Canadian citizens.

Prompted by Ontario? Province says no

If the law passes, which is likely, provinces could then restrict benefits to people not on that list, including most foreign nationals.

But temporary foreign workers, students and visitors are all required to prove they can financially support themselves before coming to Canada, leaving only refugee claimants exposed to the possibility of restricted benefits.

It's in those first few months in Canada while they await a decision on their claim that their needs are acute, the groups said in a open letter released Tuesday.

"Access to social assistance is vital to sustain and rebuild lives," the letter reads.

"Without that source of support, many will be unable to feed, house, or clothe themselves and their families, putting further pressure on already overburdened charities and shelters."

Immigration officials have told MPs and senators the policy change was prompted by conversations with the province of Ontario on refugee system reform, but a spokesperson for the Ontario government disputes that they ever asked.

It's not about the provinces, said Dr. Ritika Goel of the advocacy group Health For All, one of several activists who delivered copies of the letter to the finance minister's constituency office.

"It's about a precedent, it's about opening the door to something and sending a message about refugees," Goel said.

Cutting off welfare abuse

During committee hearings on the issue Tuesday, Conservative MP Gerald Keddy elaborated on his party's rationale in a heated exchange with Biss.

"What it actually allows is those who are abusing the system — false refugees or fake asylum claimants — to lose their social assistance," Keddy said.

"And what about those people who will be successful in their claims?" Biss shot back before the conversation was ended by the committee chair.

Keddy's language mirrors that of the government in its ongoing efforts to revamp the refugee system in Canada.

The Conservatives used the same justification — discouraging bogus claims — in their controversial decision in 2012 to slash health care coverage for refugee claimants.

That policy change ended up in court, where it was struck down as unconstitutional — a decision the federal government is appealing.

The changes to welfare eligibility could face the same fate, Biss said.

"There are a lot of ways this bill could be challenged, most fundamentally in line with the charter and the human rights violations that will occur if this bill is passed."