Three Conservative senators who travelled to the U.S. to speak with federal government officials about Canada's plans to legalize recreational marijuana use are trying to undermine the relationship between Ottawa and Washington, says the federal Liberals' representative in the Senate.

Calling the trio's discussion with U.S. Attorney General Jeff Sessions "highly unusual," Sen. Peter Harder criticized Senators Claude Carignan, Pierre-Hugues Boisvenu and Denise Batters over their recent D.C. visit.

"The senators who undertook this visit do not speak for Canada," he said in an email to CBC News.

"I regret that this includes meeting with American cabinet officials in an effort to undermine the government of Canada's relationship with the American administration."

Sen. Batters dismisses the accusation.

"Absolutely, that was not what we were going there to do," she said, adding the group never suggested it spoke for the Canadian government.

Denise Batters was one of three Conservative senators who went to Washington D.C. this week where they spoke with U.S. Attorney General Jeff Sessions about Canada's plan to legalize cannabis. 9:18

The three senators said they went to Washington D.C. on Tuesday to try to get answers to outstanding questions about the impact of marijuana legalization on policy files such as border crossings and cross-border trade. Batters said they went south because they were not satisfied with the responses they've gotten to date from Canadian cabinet ministers.

"We always maintain a respectful tone with our U.S. counterparts. This was in no way a partisan trip. When senator Harder says that we don't speak for Canada — we were there to speak for Canadians," Sen. Batters said.

Voicing concerns

In addition to meeting with Sessions, the Conservatives said they spoke with officials from the Department of Homeland Security, U.S. Customs and Border Protection and political advisers for several U.S. senators and congressional representatives.

All three Conservative senators are vehemently opposed to Prime Minister Justin Trudeau's plan to legalize marijuana. Sen. Boisvenu called the proposed legalization a "piece of shit", though he later apologized for his choice of words.

Jeff Sessions is no fan of pot legalization either. He has instructed federal prosecutors to more aggressively enforce drug laws in states that have legalized cannabis, arguing that "marijuana is a dangerous drug."

"Our trip was about much more than one meeting," said Batters.

Stockwell, Supriya, Sally and Chris weigh in on Conservative senators' trip to the U.S. to discuss legal pot. 6:38

She said she and her colleagues worry about what could happen to Canadians who try to cross the U.S. border with marijuana residue on their clothes or vehicles. She also expressed concerns about potential border delays, something Public Safety Minister Ralph Goodale said he hoped could be avoided when speaking before a Senate committee last month.

The U.S. Department of Justice declined to comment on the discussion.