Wellington's infrastructure flaws are back in the spotlight.

Yesterday's flooding and heavy rain left the capital all but cut off when the two state highways in and out of Wellington were closed to traffic and rail services were cancelled.

Labour Leader Andrew Little says it highlights the need for the Transmission Gully highway connection.

"It must be necessary for the capital city to have alternative forms of entry and egress from the city, whether it's weather, earthquake, whatever natural disaster."