Canada's government has introduced a bill to parliament in Ottawa to legalise same-sex marriage.
A small majority of Canadians are in favour of same-sex marriage
As he announced the bill, Justice Minister Irwin Cotler defended it as a critical step in constitutionally defending minority rights.
Same-sex marriage is legal in several provinces, but the proposed law is still controversial.
The issue has split the governing Liberal party, with several MPs vowing to vote against the bill.
"The government cannot and should not pick and choose which rights they will defend, and which rights they will ignore," Mr Colter told a news conference in the capital.
"If the fundamental rights of one minority can be denied, if one prohibited form of discrimination under the charter can be waved away, so potentially can those of others.
"This legislation will respect and defend the charter rights of all Canadians," he added.
Nevertheless Roman Catholic groups in Canada have joined with others including Muslim and Orthodox Jewish groups to lobby against the bill.
Politicians are divided, including those in the minority government headed by Liberal Prime Minister Paul Martin.
A survey in Tuesday's Globe and Mail daily newspaper suggested that 139 MPs backed the bill, 49 were undecided and 118 MPs opposed it.
The opposition Conservative leader, Stephen Harper, says he defends the traditional definition of marriage as between a man and a woman.
Opinion polls show that a small majority of Canadians support the right of gay and lesbian couples to marry.
In some ways, Canada's central government is simply catching up with High Court decisions in eight of the country's 13 provinces and territories where gay marriage is perfectly legal, says the BBC's Lee Carter in Toronto.
If passed, the legislation would put Canada on quite a different course to its powerful neighbour to the south, our correspondent adds.
In the United States, President George W Bush is seeking a constitutional amendment to enshrine the traditional heterosexual definition of marriage.