Former prime ministers Helen Clark and Sir John Key have joined forces in support of relocating Auckland's port to Whangārei.

Photo: RNZ / Claire Eastham-Farrelly / Rebekah Parsons King

The pair are part of Waterfront 2029 - a new campaign backing Northport, at Marsden Point near Whangārei.

Ms Clark and Sir John spent their political careers on opposite sides of the political divide but are now collaborating on a social media campaign being rolled out by Waterfront 2029.

While neither the government nor the National Party have picked a side at this point, New Zealand First has long campaigned for the shift.

A Waterfront 2029 spokesperson, Michael Goldwater, said Auckland had a once-in-a-generation opportunity to unlock the values of its waterfront for its people and ratepayers.

"Great waterfront cities grow around ports," Mr Goldwater said.

"But as those cities grow, their ports move to less densely populated areas and less expensive land. Auckland is now decades behind. The time has come to stop the endless report writing and for our government to make final decisions about the future."

Mr Goldwater said no further development of Auckland's used-car and container port was viable and described the port as "sunset infrastructure".

Prime central Auckland land was being used for something that could be done elsewhere, more efficiently, he said.

Ms Clark said the move would be a win-win for both Northland and Auckland.

She said it would provide regional development and employment benefits for Northland and could realise benefits for the development of Auckland as a world-class city.

Sir John said it was a sensible initiative.

The Waterfront 2029 campaign hopes to raise $250,0000 to get it started.