Prime Minister Stephen Harper called on NDP MP Libby Davies to resign as her party's deputy leader after she suggested Israel has been occupying territory since the country came into existence.

"Mr. Speaker, this is a fundamental denial of Israel's right to exist," Harper said in the House of Commons on Tuesday. "It repeats the kind of comments that were made by Helen Thomas on which she was forced to resign and the member of the NDP who said those should be forced to resign as well."

Thomas was the veteran White House correspondent who resigned after saying Jews in Israel should "get the hell out of Palestine" and "go back to Poland, Germany, America and everywhere else."

Liberal foreign affairs critic Bob Rae also denounced Davies' comments.

"To deny the state of Israel's right to exist and to propose an international campaign of boycotts, divestments and sanctions against a legitimate member of the world community for over 60 years is to reveal a level of hostility and ignorance that is truly breathtaking," Rae said in a written statement.

In a media scrum later, Rae argued that Davies' comments were not simply a slip of the tongue and called for her to step down as deputy leader.

Earlier this month, Davies was interviewed at a rally in Vancouver and asked if she believes the occupation in Israel began in 1948 or 1967. After hesitating, she answered:

"Forty-eight. I mean, it's the longest occupation in the world. But I mean, I'm not going to argue numbers. It's too long, right?" She went on to say, "I mean, this is the longest occupation in the world. People are suffering. I've been to the West Bank in Gaza twice so I've seen for myself what's going on."

The state of Israel was established in 1948.

In the video, Davies is also asked if she supports the international campaign of boycotts, divestments and sanctions against Israel (known as the BDS movement).

"I haven't even actually gone that far. You gotta understand, I'm probably the strongest supporter in Parliament. There is virtually no information in the political arena or understanding about the BDS movement. People are actually afraid to speak out on this issue.… Elected people who are sympathetic are actually afraid to speak out," Davies answers.

Later in the video, Davies says she personally supports the BDS movement, adding, however, that she's not "someone who's there" but is instead a Canadian politician demanding the Canadian government speak out more on the issues.

The interview was posted on YouTube.

Since her comments were made public, Davies has posted on her website a letter she sent to the editor of The Ottawa Citizen.

"My reference to the year 1948 as the beginning of the Israeli occupation of Palestinian territory was a serious and completely inadvertent error," she wrote. "I apologize for this and regret any confusion it has caused. I have always supported a two-state solution to the ongoing Israeli-Palestinian conflict and have never questioned Israel's right to exist and the Palestinians' right to a viable state."

NDP Leader Jack Layton defended Davies Tuesday.

"Libby Davies has apologized and did so immediately around the serious mistake about a date. She has never and our party has never, nor would we ever deny that Israel not only has a right to exist but a right to exist in secure borders in a safe context," he said.

Layton added that the party does not support the BDS proposal.