New Zealand is set to have its third official language from today -- something the hearing impaired have been waiting 20 years for.

The passing of legislation today will make sign language an official language, along with English and Maori.

It will mean people will be able to use NZ Sign Language in legal proceedings, including in court.

Disability Issues Minister Ruth Dyson said the deaf community had been seeking recognition of NZ Sign Language for 20 years.

It was used by about 28,000 people here. An estimated 7000 people in New Zealand are deaf.

Members of the deaf community plan to be in Parliament for the third reading today of the New Zealand Sign Language Bill.

Sign language interpreters will provide simultaneous translations in the House which will be relayed on screens in the Beehive foyer, where a function is planned to celebrate the event, and broadcast to the internet.