Stephen Harper has come out against his successor's handling of NAFTA negotiations with the United States, with the former prime minister declaring the negotiations in real peril in a memo titled, "Napping on NAFTA."

The memo was obtained by The Canadian Press and it criticizes the Trudeau government in several areas: For too quickly rejecting U.S. proposals, for insisting on negotiating alongside Mexico, and for promoting progressive priorities like labour, gender, aboriginal and environmental issues.

The former prime minister says he was worried by what he heard during a recent trip to Washington, where he discussed NAFTA at an event but did not publicly share his misgivings about the Trudeau government.

Stephen Harper blasts Trudeau government's handling of NAFTA negotiations2:12

"I came back alarmed," said the Oct. 25 letter signed by Harper, and sent to clients of his firm Harper & Associates.

"I fear that the NAFTA re-negotiation is going very badly. I also believe that President (Donald) Trump's threat to terminate NAFTA is not a bluff … I believe this threat is real. Therefore, Canada's government needs to get its head around this reality: it does not matter whether current American proposals are worse than what we have now. What matters in evaluating them is whether it is worth having a trade agreement with the Americans or not."

The current government was not pleased by the letter.

Foreign Affairs Minister Chrystia Freeland described Harper's position as "capitulation."

Officials in Ottawa accused the former prime minister of essentially negotiating in public — against the government of Canada. They called the release of the two-page note ill-timed and perplexing.

"This is a gift to the Americans," said one current Canadian official.

"There's nothing Wilbur Ross and Robert Lighthizer [from the Trump administration] want to see more than prominent Canadians standing up to suggest making concessions to the Americans. Make no mistake: Wilbur Ross and Robert Lighthizer will be very happy with this letter."

Lisa Raitt, the Conservatives party's deputy leader who served in Harper's cabinet, said the former prime minister was just "putting his thoughts down on paper" and that "a lot of people agree with him."

"He's just putting his point of view forward on how to approach it, and what he would be advising if he were in the spot, and I think it's very valid for him to do that," she told CBC News on Saturday.

Lisa Raitt on Harper's leaked memo criticizing Liberals' handling of NAFTA renegotiations5:59

Being stubborn

The memo accuses the Canadian government of stubbornness on several fronts.

First, it suggests Canada has been too quick in rejecting American proposals as a "red line," or "poison pill." He said such knee-jerk refusals are only a viable strategy if you truly believe Trump cannot cancel NAFTA — an assessment Harper does not share.

Second, he suggests the government made a tactical error by co-operating too closely with Mexico. He says Trump campaigned on constant complaints about Mexico, not Canada, and Harper appears to suggest it was unwise of the Liberals to insist upon renegotiating a trilateral NAFTA: "How did we get ourselves in this position? … The elephant is Mexico … In fact, the U.S. is both irked and mystified by the Liberals' unwavering devotion to Mexico."

Third, he criticizes the Liberals for pursuing their progressive trade policies in these talks: "Did anyone really think that the Liberals could somehow force the Trump administration into enacting their agenda — union power, climate change, aboriginal claims, gender issues? But while the Canadian government was doing that, the Americans have been laying down their real demands."

'It is a bit sad'

Finally, he accuses the Liberals of bungling other disputes over lumber and airplanes. Harper says the Liberals passed up on a chance to renew the softwood lumber agreement in exchange for supporting the Trans-Pacific Partnership, and he says their subsidies to Bombardier set the stage for huge tariffs today.

The Liberals say that last point about softwood lumber is based on a falsehood.

They say there was never a softwood settlement on the table, and that claims to the contrary are wrong. As for the progressive trade agenda, they point to recent polls showing that improved labour and environmental standards in NAFTA are exceptionally popular in the U.S., and they say some of these provisions could help win crucial ratification votes from Democrats to actually get an eventual deal through the U.S. Congress.

"It is a bit sad," said a second Canadian official, requesting anonymity.

"He's basically saying we need to make more concessions to the Americans, turn our backs on workers, turn our backs on softwood workers … put thousands of aerospace workers out of work."

Stephen Harper says Trudeau government is 'Napping on NAFTA' | Sunday Scrum10:26

With files from CBC News