Australia’s longest serving Labor prime minister, Bob Hawke, has passed away.

"Today we lost Bob Hawke, a great Australian – many would say the greatest Australian of the post-war era," Mr Hawke's wife Blanche d'Alpuget said in a statement on Thursday.

"Bob was dearly loved by his family, and so many friends and colleagues. We will miss him.

"The golden bowl is broken."

The charismatic prime minister led the Labor party to victory in four consecutive elections from 1983 to 1991.

His death comes just two days before 18 May elections.

On Wednesday, he wrote an open letter urging Australians to back opposition Labor leader Bill Shorten.

"With his passing, the labor movement salutes our greatest son... and Australians everywhere remember and honour a man who gave so much to the country and people he cared for so deeply," Mr Shorten said.

“Every Australian carries a monument to Bob Hawke with them, their Medicare card. A green-and-gold promise that the health of any one of us, matters to all of us."

He led the country through a transformative period, including the establishment of Medicare, Landcare and the Prices and Income Accord.