Open this photo in gallery A group of asylum seekers wait to be processed after being escorted from their tent encampment to the Canada Border Services in Lacolle, Que. on Aug. 11, 2017. CHRISTINNE MUSCHI/Reuters

The number of asylum seekers crossing into Canada from the United States through unofficial ports of entry is continuing to increase, according to federal government officials, who estimate about 2,500 people walked across the border in April.

Immigration officials made the estimate during testimony to the House of Commons immigration committee on Thursday, after Conservative MP Michelle Rempel took them to task for not knowing the exact number of people who crossed into Canada between legal border crossings in April.

Mike MacDonald, an associate assistant deputy minister at the immigration department, apologized for not having the exact numbers, but said that according to the data he had so far, he would guess that 2,500 people entered Canada between legal border posts in April.

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“We can always give data a few days after the first of each month, but it will be imperfect,” Mr. MacDonald said.

“We like to clarify and clean our data as much as possible.”

Asylum claim data is normally posted on the immigration department’s website halfway through the following month, meaning that officials would not post the April numbers until around May 15.

That explanation wasn’t good enough for Ms. Rempel, who put forward a motion calling on the government to table the numbers by the end of the week. She said officials’ inability to provide the data is “somewhat of an affront to democracy.”

“It does not instill confidence in the Canadian public that the officials who are the most senior in our government, sitting in front of our committee, in front of a table full of parliamentarians for a briefing specifically on so-called irregular border crossings, that you would not have the number for April,” Ms. Rempel said.

After some debate among MPs, the Liberal-majority committee amended the motion, calling on the government to table the data by May 11 at the latest.

The estimate of 2,500 border crossers for April far surpasses the 859 people RCMP intercepted at unofficial ports of entry along the U.S. border in April, 2017.

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Last year, the RCMP intercepted 20,593 people between legal ports of entry along the entire Canada-U.S. border. The most recent data on the immigration department’s website indicate that trend continued into 2018, with 5,052 border crossings from January to March alone.

MPs also grilled officials on the government’s continuing high-level talks with the United States over a border agreement to manage asylum seekers. Earlier this week, the U.S. Department of Homeland Security confirmed it is reviewing a Canadian proposal to amend the Safe Third Country Agreement (STCA), which requires Canada and the United States to refuse entry to asylum seekers who arrive at official ports of entry along the shared border, as both countries are considered safe for refugees.

Officials detailed those talks on Thursday, saying three major points are up for discussion with the United States. Mr. MacDonald said they are discussing the need to update the 14-year-old agreement and introduce the use of modern technologies to identify asylum seekers, such as biometrics, at the border. He said officials are also discussing the principle on which the pact is based on – that asylum seekers ask for protection in the first country they can do so in.

Reuters reported on Tuesday that the government wants the agreement to apply to the entire Canada-U.S. border, something senior government officials have yet to publicly confirm that.

However, Mr. MacDonald said the government has not expressed a desire to invoke article 10 of Safe Third Country Agreement, which would allow it to suspend the agreement for up to three months with written notice.