Souter Investments, the global public transport company owned by Scottish transport entrepreneur Brian Souter, is investing $12 million in 15 new double-decker buses for Auckland.

The double decker buses are shorter than a regular commuter bus yet carry nearly twice the number of passengers - 90 rather than 48. They will be used on one of the city's most congested routes, the east Auckland corridor between Botany and downtown Auckland serviced by Howick - Eastern, which is owned by Souter Investments.

All but two of the buses are being built in Tauranga by Kiwi Bus Builders and Alexander Dennis with the first two due to be ready for service by October. The rest are likely to take another four to five months.

Last year Auckland Transport chief executive David Warburton told a public meeting that the south-eastern areas was the worst served by public transport in the city.

Howick - Eastern Buses general manager Sheryl Otway said the double deck businesses set a new standard for Auckland public bus transport because of features such as free wi-fi, power points and USB ports.

Another operator, Ritchies Transport, already uses double deck buses on the northern motorway route.

Otway said the new buses will mean increased frequency of services on the busy east Auckland route as they're additional to the existing 163 fleet, though some older buses will be deployed to other routes once the new vehicles arrive.

The new vehicles are similar to the buses used by online bus service ManaBus.com which Souter launched late last year. Souter Holdings also owns Fullers Ferries and the Wellington-based bus service, Mana Coach Services.

At the time of the launch Souter said his company had invested $100 million in its New Zealand bus and ferry services over the past seven years, including $5 million investment in the six-bus fleet for ManaBus.com.