Deputy NSW Premier and Transport Minister John Watkins has resigned after 13 years in the state politics, prompting a cabinet reshuffle.

Mr Watkins said the decision came to regain the “work-family balance”. He is expected to take up the role of chief executive at Alzheimer’s Australia.

“After more than 20 years in public life, I think it is the right time to move on to pursue new challenges and to give others the opportunity of experiencing the privileges that I have in my roles in public life,” he told the Fairfax.

“This job comes at some cost, both physically and emotionally and it impacts very strongly on your family and loved ones.”

Mr Watkins, who had recently lost both of his parents, said the public spotlight had been both “exhilarating and exhausting”.

“In recent times I have been counting these costs…I believe it is time to get that work-family balance back right,” he said.

Premier Morris Iemma paid a tribute to Mr Watkins, describing him as “a voice of reason and commonsense”.

“John’s been one of the outstanding figures of modern Labor politics, a man who tackled some of the most demanding portfolios in government and never lost his sense of decency and compassion,” he said.

Mr Watkins has been regarded as Premier Morris Iemma’s successor, but it is understood tensions with NSW Treasurer Michael Costa have become intensified recently over the plan to build a $17 billion metro line across north-west Sydney.

His unexpected departure has triggered a major cabinet reshuffle. Mr Iemma and Mr Costa have been ousted, with Water Minister Nathan Rees and Labor MP Carmel Tebbutt set to take over the new leadership team. 

It is unclear who would take over the transport department, which controls Railcorp and the freight lines in metropolitan Sydney.