Toronto Archbishop Aloysius Cardinal Ambrozic sent an open letter to Prime Minister Paul Martin, urging him to block same-sex marriage by invoking the Canadian Constitution’s notwithstanding clause, The Globe and Mail reported Wednesday.

The clause, which can be employed to override the Charter of Rights and Freedoms, is a temporary measure that needs renewal every five years.

Cardinal Ambrozic says this five-year period would allow for more debate and give Canadians the opportunity “to observe the social experiments now under way” in countries where same-sex marriage is legal, such as in Belgium and the Netherlands.

Conservative Party Leader Stephen Harper disagrees with the cardinal, saying that the notwithstanding clause is “not necessary.”

"It is necessary for the federal government to adopt legislation that protects the traditional definition and protects religious freedom,” he told the Canadian Press.

The Conservative Party is planning to launch a national campaign to defend traditional marriage with ads in multicultural newspapers and religious publications.

Meanwhile in India, the Canadian Prime Minister fielded questions from reporters after Joginder Singh Vedanti, the spiritual leader of the Sikhs, said: "Same-sex marriage originates from a sick mind."

"This is a question of civil marriage, not of religious marriage," Martin told reporters.

“I would point out that we are a country of ethnic and religious minorities,” he continued. "And the purpose of the Charter of Rights is to protect minorities, to protect them against the oppression of the majority."

Martin’s Liberal Party is expected to table a same-sex marriage bill in February and pass legislation by summer.

If Parliament defeats the bill, same-sex marriages will still be legal in Ontario, Quebec, British Columbia, Nova Scotia, Newfoundland, Manitoba, Saskatchewan and Yukon, where provincial courts ruled that the traditional definition of marriage is unconstitutional.