WINNIPEG - First Nations leaders and NDP MP Niki Ashton are demanding the federal government act on an "epidemic" level of missing and murdered aboriginal women.

"Aboriginal women in Canada are at risk and our response as Canadians is woefully inadequate," said Ashton Friday.

The Churchill MP and NDP critic for the status of women joined Manitoba Keewatinowi Okimakanak Grand Chief David Harper and others to demand the launch of a national inquiry before July 10. A detailed federal plan to address the issue might also be accepted.

"We need some response stating this is how we're going to fight this battle," said Harper.

Alleged serial killer Shawn Cameron Lamb was charged with the murders of Winnipeg women Tanya Nepinak, Carolyn Sinclair, and Lorna Blacksmith earlier this week, sparking calls for an inquiry.

Harper said more than 80 aboriginal women are currently murdered or missing in Manitoba, with 600 across Canada.

If Ottawa does not respond by July 10, First Nations leaders will launch an international campaign to push for their demands.

Ashton said a Royal Commission on Aboriginal Peoples and Manitoba's aboriginal justice inquiry produced results in the past. But she believes an inquiry devoted entirely to missing and murdered women could help prevent tragedies and address factors that make aboriginal women vulnerable to violence.

Manitoba government ministers recently rejected calls for a similar inquiry but said one might be possible in the future.

The Federal Justice Minister's office also didn't commit to an inquiry Friday. It stated a $10-million plan to enhance police support for missing persons cases and boost victims' services is already in place.

"Our government attaches great importance and urgency to addressing the issue of missing and murdered aboriginal women. Our heartfelt sympathies go out to their grieving families," Julie Di Mambro, a justice spokeswoman, wrote in an email.