The House of Lords has crushed an attempt to kill off the gay marriage Bill by 390 votes to 148 - a majority of 242 in favour of same-sex weddings.
In total more than 90 peers spoke during the marathon two-day debate, with those opposed warning gay marriage would lead to polygamy, incest and even the decline in heterosexual weddings.
Tory Lord Eden, the nephew of former prime minister Anthony Eden, said the Bill had been "bounced" on peers.
"It has sent shockwaves throughout the country, it is damaging, divisive and destructive," he said.
Lord Hylton, one of the few remaining hereditary peers, said he was even unhappy that the word 'gay' had "been appropriated by a small and vocal minority of the population" and could no longer be used in its "original and delightful meaning".
And Lord Dannatt, who was chief of the general staff from 2006 to 2009, said the Bill was an "abuse of the democratic process".
It is highly unusual for the House of Lords to attempt to kill off a piece of government legislation that had received the backing of the elected Commons.
But Independent crossbencher Lord Dear demanded on Monday that the Bill be refused a second reading, following fierce opposition to the legislation from dozens of Tory backbenchers and religious leaders.
He warned that the "ill-considered Bill seeks to overturn centuries of tradition, heedless of public opinion and the views of religious leaders, and blind to the laws of unintended consequences".
David Cameron has personally backed the legislation despite it causing a deep split in the Conservative parliamentary party - the majority of Tory MPs voted against it.
Speaking in the Lord for the government, Baroness Stowell of Beeston hailed the legislation as a "force for good" which would strengthen the institution of marriage.
Lady Stowell urged peers to back the Bill and assured them that religious organisations would not be compelled to perform same sex marriages if they did not wish to.
And Lord Fowler, a former chairman of the Tory Party who supports the Bill, told peers that gay people, who continued to suffer discrimination, had the right "to expect what we all expect; nothing more, but certainly nothing less.
"Parliament should value people equally in the law and enabling same-sex marriage removes a current inequity," he said. "For some of us, that is a fundamental moral issue."