Same-sex marriage is not legal in Switzerland, though same-sex couples can enter into a civil partnership after the move was approved in a 2005 referendum.
While many MPs – and, according to a 2015 survey, a majority of the Swiss public – are in favour of marriage equality, hardline conservative MPs have tried to block moves towards it.
Speaking in parliament SVP MP Yves Nidegger said the word marriage was historically linked to the fact that a couple can procreate, reported news agencies.