OTTAWA 芒鈧珺次元官网网址� Prime Minister Justin Trudeau defended his government's proposed legislation to expand border preclearance at Canadian airports and other crossings Wednesday as the opposition New Democrats pushed to stop the bill in its tracks.

The NDP argued the bill doesn't take into account what it called "the climate of uncertainty at the border" created by the Trump administration's recently adopted immigration policies.

But Trudeau suggested it's better to be cleared for entry into the United States while in Canada, because travellers are protected under the Canadian charter of rights, as opposed to American laws.

Bill C-23, the Preclearance Act, came up for second reading in the House of Commons on Tuesday.

Introduced by Public Safety Minister Ralph Goodale last June, it would replace and expand provisions of the Air Transport Preclearance Agreement signed between Canada and the United States in 2001.

The two countries signed a new agreement in 2015 to expand border clearance and proponents say measures included in the bill will speed the flow of people and goods across the border.

Under preclearance, travellers don't have to pass through customs in the U.S., because they've already done so before departing Canada.

U.S. Customs and Border Protection officers do not have peace officer status in Canada and cannot make arrests and that would not change under the proposed system. If an arrest were to be made, the U.S. officer would hold the person until a Canadian law-enforcement officer arrived.

However, the bill would alter powers in at least one notable respect. Currently, someone could simply walk out of a preclearance area should they change their mind about crossing the border into the U.S.

Under the new system, a U.S. border officer could ask the person to identify themselves and say why they were withdrawing. If the American officer suspected the person had violated Canadian law, the individual could be questioned further or even detained. Should the officer come to believe a Canadian law had been breached, the person would be handed over to Canadian authorities.

Any U.S. preclearance activities in Canada would have to be carried out in a manner consistent with Canadian law, including the charter and the Canadian Human Rights Act.

New measures would be reciprocal, meaning they would apply equally to any Canada Border Services Agency officers conducting preclearance in the U.S.

Critics have concerns about the legislation, arguing that it would lead to the erosion of rights of people travelling both to the United States and Canada.

The bill "does not address Canadians' concerns about being interrogated, detained and turned back at the border based on race, religion, travel history or birthplace as a result of policies that may contravene the Canadian Charter of Rights and Freedoms," NDP public safety critic Matthew Dube said in putting forward a motion that could effectively kill the bill.

"What we're seeing right now is a reality where people are being discriminated against at the border," Dube told reporters.

"Given that reality, we have serious concerns about these new, extra powers being given to American agents."

Dube cited the example of a Vancouver man who said he was turned away from a B.C. border crossing after a U.S. Customs and Border Patrol officer scoured his cellphone for recent messages.

The officer suspected the man was a sex worker based on one email message, the man reportedly told Daily Xtra.

On his way into a Liberal caucus meeting Wednesday, Trudeau suggested it's better to be cleared for travel while still on Canadian soil.

"If we didn't have preclearance in Canada, people would be passing customs in the United States," said Trudeau.

"And in the United States, American laws dominate and control the behaviour of people in border crossings.

"When you're doing preclearance in Canada, the Canadian Charter of Rights and Freedoms and Canadian laws are in place, so there is extra protection."

Terry Pedwell, The Canadian Press