Liberal Leader Paul Martin warned Monday that a Stephen Harper-led government would pose a threat to minority rights.

Martin said the Conservative leader believes the Charter of Rights and Freedoms has "deep flaws."

"The reason for the Charter and the reason I am such a strong supporter of the Charter ... is that we have to ensure that minority rights are protected when challenged by the majority," Martin said.

Paul Martin pauses for a moment prior to a television interview in Ottawa (CP PHOTO)

Harper has refused to rule out the use of the nothwithstanding clause, under which Parliament can override the Charter. Martin has said he would not use the notwithstanding clause.

"And if what you're prepared to do is use the notwithstanding clause, then what you're saying essentially is minority rights can be subjected to the will of the majority.

"And I've got to tell you that is not the kind of country I believe in, nor do I think it's the kind of country that Canadians believe in."

When asked about abortion, Martin says he would not allow MPs to remove rights already established in the Charter through private bills.

Although Harper has said he would not introduce abortion legislation, he has said he would allow the issue to be put to a free vote in the House of Commons.

"Never, never will I allow the rights of women to be trampled on by legislation in that area," he said.

Harper's comments bridled Minister of Justice Irwin Cotler who noted in a news release that the Charter is admired throughout the world, and has been a model for other constitutions, such as South Africa's Bill of Rights.

The Charter, he added, "means that no Canadian can have their house searched without the approval of a judge. It means that every woman has the ultimate say over her own body. It means that minorities will be able to speak and learn in either of Canada's two official languages.

The aggressive Liberal attack on Harper marks a new phase of the Liberal campaign, which is trying to push ahead of the Conservatives in the remaining weeks before the election by contrasting the ideological differences in election platforms.

"In fact, this is going to come down to values," said Martin. "Now that the platforms are out, people are going to judge the values of the party leaders and the values of the parties themselves."

Martin admitted that the recent dip in Liberal support has not surprised him. "I knew that the numbers would be very tight from the beginning," said Martin.

He expects voters to team with the Liberals once they judge which of the two leaders they can trust to lead the country.

NDP Leader Jack Layton took aim at the Conservative's view on abortion and same-sex marriage warning Canadians that Harper would "turn back the clock" on various social issues.

"If the Liberals don't deserve a fourth term, the Conservatives sure don't deserve a first," said Layton.