The actions of the owners of a dog thrown off the Wairoa Bridge are being described as "appalling".

Tauranga SPCA animal welfare officer Anna Porteous says the owners of an adult dog hit an all-time city low after ditching their animal off the bridge overnight.

Tauranga SPCA animal welfare inspector Anna Porteous with the adult dog thrown off the Wairoa Bridge overnight. Photo: Tracy Hardy.

At about 11pm witnesses saw what is believed to be a Toyota Estima van stop briefly on the bridge before hearing a splash.

The van was travelling along State Highway 2 from Katikati before turning around at the bridge.

Anna says the dog managed to swim to shore before witnesses lassoed a rope around its neck.

They also attached a torch to the dog so if it moved they could follow it in the dark.

A SPCA emergency team was later called to retrieve the adult female Shar-Pei Labrador cross, chocolate in colour.

Anna says the dog is at the Tauranga SPCA in 'okay condition” apart from being a little timid and scared.

She says it's common for people to dump puppies to be found later, but it's rare for fully grown dogs to be thrown off a bridge.

'It is appalling behaviour to throw a dog off a bridge and carry on with no concern. This is a new low,” says Anna.

Tauranga SPCA are appealing for anyone who may know the dog or were in the vicinity of the Wairoa Bridge at the time of the incident.

'They were coming from Katikati; they went over the over the bridge; they stopped and turned around and went back to Wairoa Road; stopped turned around again and went to the middle of the bridge and threw the dog off.

'Even if people don't come forward and tell us about the incident someone will know who this was and hopefully name and shame them a bit.

Anyone with any information are to call the Tauranga SPCA on 07 578 0245.

The SPCA will offer a reward for information leading to prosecution.