A pioneer of the same-sex marriage movement has admitted that multi-partner marriage is the next logical step in the evolution of the institution of marriage.

Boris Dittrich, a former Dutch MP sometimes called the father of the global campaign to legalise same-sex marriage, told a French online magazine, Yagg, that there was now a movement in the Netherlands to legalise polygamy.

Asked if complete “marriage equality” had been achieved in Holland, Dittrich said that it had, but that there was now a debate beginning about polygamy.

Dittrich said: “There is now a discussion in the Netherlands that sometimes people want to marry with three people or maybe more, but that’s the beginning of something completely new and that will take a lot of years.

Last year, a public notary in Brazil sparked controversy by permitting a civil union between two women and a man.

Claudia do Nascimento Domingues, who conducted the ceremony in the Brazilian province of Sao Paolo, insisted that Brazilian law did not prohibit such a three-way arrangement and that such arrangements should enjoy the same rights as traditional pairs.

In 2010, the High Court here heard the case of a Muslim man who demanded that the State recognise his polygamous marriage.

The man was from Lebanon, where polygamy is permitted. He was married to two women and has been granted Irish citizenship.

The Department of Justice refused to grant the man’s first wife a visa. The man entered Ireland with his second wife and claimed asylum. His first wife did not arrive until much later. The man had children with both women.

The High Court turned down his plea.

In 2011, the Supreme in the Canadian province of British Columbia heard a case to decide whether polygamous marriage as practiced by a Mormon sect, is protected by the Canadian constitution’s guarantee of freedom of religion.

The court ruled that polygamy was bad for children and bad for women and the law upholding the ban was therefore constitutional.

However, traditional marriage advocates said it showed the pressure the traditional definition of marriage is now under in the West.

In July 2011, the youth wing of the Finnish Green Party proposed the legalisation of polygamy.

The Federation of Green Youth and Students (ViNO) said it believed that Finnish marriage laws “discriminate” against those who want multiple spouses. Party secretary for the Greens, Panu Laturi commented to Finnish newspaper Iltalehti that the main party does not support its youth wing’s views on this issue.