The Vatican is digging in after gay marriage initiatives scored big wins this week in the US and Europe.

It vows to never stop insisting that marriage can only be between a man and a woman.

In a front-page article in Vatican newspaper L'Osservatore Romano, the Holy See sought to frame itself as the lone voice of courage in opposing initiatives to give same-sex couples legal recognition.

In a separate Vatican Radio editorial, the pope's spokesman asked sarcastically why gay marriage proponents do not now push for legal recognition for polygamous couples as well.

According to Catholic teaching, it holds that homosexuals should be respected and treated with dignity but that homosexual acts are "intrinsically disordered".

The Vatican also opposes same-sex marriage, insisting on the sanctity of marriage between a man and woman as the foundation for society.

The Vatican's anti-gay marriage media blitz came after three US states approved same-sex marriage by popular vote in the election that returned Barack Obama to the US presidency.

Spain has upheld its gay marriage law and France has pushed ahead with legislation that could see gay marriage legalised early next year.

L'Osservatore Romano wrote that Catholics were putting up a valiant fight to uphold church teaching in the face of "politically correct ideologies invading every culture of the world" that are backed by institutions like the United Nations, which last year passed a non-binding resolution condemning anti-gay discrimination.

Vatican spokesman the Rev Federico Lombardi, for his part, said gay people can have their rights protected by means other than through legal marital recognition.

He stressed that children should have a right to say they have a father and a mother.

"If not, then why not contemplate freely chosen polygamy, and naturally so as to not discriminate, polyandry?" he asked sarcastically.

Polyandry is when a woman has two or more husbands.

"As a result, don't expect the church to stop insisting that society recognises a specific place for marriage between a man and woman," he said.

The US election had been closely watched at the Vatican because of the strong divisions that erupted during the campaign between the Obama administration and US bishops over gay marriage, which Mr Obama endorsed in May.

The administration and bishops clashed more vehemently over Obama's health care mandate requiring nearly all US health insurance plans to cover contraception, which the church opposes.

The US Conference of Catholic Bishops said the contraception mandate, which exempts houses of worship but applies to faith-affiliated employers, is a violation of religious freedom.

The Vatican's reaction to Mr Obama's re-election was tinged with such lingering criticism, with Pope Benedict XVI congratulating Mr Obama and praying that the ideals of freedom and justice continue to be upheld.