An extended underground light rail route will be built in Auckland.

The Government has announced the supercity's light rail project will run under the city from Wynyard Quarter to Mt Roskill, before surfacing and running alongside State Highway 20 to the airport.

The selected 24km route will see trains running every five minutes from up to 18 stops and will be able to carry 15,000 passengers per hour at peak times.

The Transport Minister Michael Wood spoke to Māni Dunlop.