OTTAWA -- Three Liberal cabinet ministers came under fire Tuesday by opposition parties concerned about sweeping implications of federal pot plans set to take effect next summer.

Justice Minister Jody Wilson-Raybould, Public Safety Minister Ralph Goodale and Health Minister Ginette Petitpas Taylor testified at a Commons committee Tuesday night on the government's proposed cannabis bill.

They were met by a series of questions, including concerns raised by police on the government's July 2018 timeline to establish a legalized regime for recreational cannabis.

Last week, officials from the Canadian Association of Chiefs of Police, Ontario Provincial Police and the Saskatoon Police Service testified to the same committee they require more time to properly train officers about the new laws and more than double the number of police officers who are certified to conduct roadside drug impaired driving testing.

Officers are not the only ones concerned about the government's proposed timeline, Conservative health critic Marilyn Gladu said Tuesday, noting many provinces do not have plans in place and municipalities are worried as well.

"Why are you in such a hurry to risk public harm?" Gladu asked. "Are you willing to consider pushing off the date until all of these stakeholders are ready?"

In response, Wilson-Raybould said the government remains committed to legalizing marijuana by July 2018, noting the current legal approach is an "abysmal failure."

"We are committed to ensuring we do something about that as quickly and as appropriately as we can," Wilson-Raybould said.

"In doing so, we have taken an extremely comprehensive approach over the last two years to ensure that we ... continue to have conversations with all of our counterparts in the provinces and territories."

NDP health critic Don Davies also raised concerns about the government's plans on edible forms of cannabis.

"If prohibition doesn't work, as you said, why are you prohibiting edibles?" Davies said.

The federal government will ensure Canadians have access to dry, fresh cannabis and oils by next July, said Petitpas Taylor, adding the government agrees with a federally-appointed task force it must confront the issue.

She said, however, regulations will be required to deal with the matter, adding it will be "done in due course."

Petitpas Taylor also warned that edible forms of cannabis created a host of challenges in U.S. states where marijuana received the green light, noting a wide range of products could be legalized here.

"They weren't properly prepared to deal with it," she told the committee.

"We want to really ensure that we have the proper regulatory framework that is in place to make sure we have all the necessary tools that are in place to make sure that we get this right."

Goodale was also asked about concerns about the treatment of Canadians at the U.S. border following marijuana legalization.

"We know the United States is a sovereign country and certainly nobody is asking anybody to tell the Americans what to do," Davies said.

There are many stories of Canadians going to the U.S. border where border guards ask about the consumption of cannabis and routinely deny entry, he added.

"Are you working to try and reach an agreement with the Americans that recognizes the new legal reality or will business people and ordinary Canadians simply have to try their luck when they get to the U.S. border on July 2?" he said.

Canada is constantly raising the reality of its changing legal regime with America, Goodale responded.

"That's an ongoing dialogue and it's one we will raise at every opportunity to ensure that Canadians are treated fairly," he said.