Political parties opposed to legal aid legislation inadvertently supported the bill's third and final reading on Tuesday night.
The legislation introduces an income threshold for receiving legal aid for civil cases and allows applications to be declined if the applicant is already in arrears.
It has only passed by a narrow margin in previous readings, with strong objections from the opposition.
The legislation has been split into six separate bills, which had their third reading together.
A misunderstanding of a call for a vote by Parliament's chairman was met by silence from opposition parties.
That means the legislation was passed without objection, which will be recorded as unanimous support in the House.
Opposition parties will appeal to have the record corrected through Parliament's business committee.