Scotland is expected to adopt the laws in the near future.
The historic step gives lesbian and gay couples access to the same rights and responsibilities as offered to heterosexual British couples married in a civil ceremony.
The vote of support comes despite fears that the bill would be blocked by peers just a day before the end of the parliamentary session.
Gay rights groups such as Stonewall feared that a large turnout for an initiative called "the hunting bill," which also re-entered the House of Lords Wednesday, could have put the success of the partnerships bill in jeopardy.
A group of Conservative peers did attempt to push through an amendment to the bill, widely viewed as a "wrecking tactic," that had already been rejected by the House of Commons.
However, the vote was won by a majority of 251 votes to 136.
"This is a historic step forward," said Stonewall's Ben Summerskill in a statement Wednesday evening. "Finally, the House of Lords has recognized that Britain is a tolerant 21st-century nation."
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