PREMIER Jay Weatherill has asserted authority over Labor's factional bosses, declaring he alone will determine the shape of a new Cabinet.

Mr Weatherill yesterday paid tribute to outgoing senior ministers Patrick Conlon and John Hill, who held the key transport and health portfolios respectively and are among Labor's most experienced MPs.

Both will leave Cabinet in a looming reshuffle and remain on the backbench until they retire at the 2014 state election.

A special caucus meeting has been called for Monday morning, where the reshuffle is expected to be rubber-stamped.

Mr Weatherill has put no time-line on his announcement but said it would be "very substantial" and "very soon".

Senior Labor sources say Right faction MP Leesa Vlahos and Leon Bignall, from the Left, are most likely to be elevated to the new Cabinet.

In the past, Labor's factions have elected replacement ministers and the leader is only allowed to allocate portfolios.

Mr Weatherill yesterday said: "I've been asked to lead and that's what I'm proposing to do".

&amp;amp;amp;amp;amp;amp;amp;ampamp;amp;amp;ampamp;amp;amp;amp;amp;amp;lt;a href="http://www.coveritlive.com/mobile.php/option=com_mobile/task=viewaltcast/altcast_code=625f772928" &amp;amp;amp;amp;amp;amp;amp;ampamp;amp;amp;ampamp;amp;amp;amp;amp;amp;gt;John Hill to resign from Cabinet&amp;amp;amp;amp;amp;amp;amp;ampamp;amp;amp;ampamp;amp;amp;amp;amp;amp;lt;/a&amp;amp;amp;amp;amp;amp;amp;ampamp;amp;amp;ampamp;amp;amp;amp;amp;amp;gt;

"I've determined who I want to have in the Cabinet ... and which portfolios they'll hold," he said.

Well-regarded Water and the River Murray Minister Paul Caica has remained silent on speculation he also will stand down from Cabinet. His department suffered deep cuts in December's mid-year Budget review.

There is also doubt about the futures of Education and Child Development Minister Grace Portolesi, who has been damaged by the sex abuse in schools controversy, and Industrial Relations Minister Russell Wortley. But a well-placed Labor source said the situation was fast-moving and far from settled. Other names being floated included Left faction backbenchers Susan Close and Kyam Maher.

Mr Weatherill would not comment on internal speculation he would cut Cabinet from 15 to 13 members.

It was understood momentum for the reshuffle increased over the weekend after The Advertiser's Saturday report that Labor insiders believed a major Cabinet change was imminent.

An adelaidenow report on Monday afternoon led Mr Conlon to publicly declare his intention, in a statement to The Advertiser, to leave politics at the 2014 election.

Mr Hill followed suit yesterday with a Twitter announcement and press conference.

The exits of Mr Conlon and Mr Hill mean two of the biggest Government portfolios must be filled.

Mr Conlon's transport and infrastructure roles may be separated and given to several ministers.

Manufacturing, Innovation and Trade Minister Tom Koutsantonis is seen by Labor insiders as likely to win a promotion. It is possible he will claim infrastructure responsibilities to pair with mining.

Mr Conlon's stewardship of the Adelaide Oval and Riverbank projects will need to be passed on, and Treasurer Jack Snelling is viewed as ready to accept additional responsibility after two years in that job.

Mr Hill yesterday said he was saddened to be leaving staff and colleagues but excited about the next chapter in his life - which would include gardening, cooking and visits to the theatre.

He listed the new Royal Adelaide Hospital development as one of his proudest achievements and called for a new debate about how health services were delivered and strong emphasis on promoting healthy lifestyles.

Names in the mix to take over the key health portfolio include Finance Minister Michael O'Brien, Social Housing Minister Ian Hunter, Tourism Minister Gail Gago and possibly even Treasurer Jack Snelling.

Before the departure of Mr Conlon and Mr Hill, Labor must find candidates for the seats of Elder and Kaurna, held on margins of 1.7 per cent and 8.7 per cent respectively, to contest the next election.

There is also speculation about the future of several long-standing Labor backbenchers, including Michael Atkinson, Frances Bedford, Robyn Geraghty and Steph Key. Preselection is to be complete by March.

Mr Weatherill yesterday said that Labor needed to look to the March 2014 election and beyond.

"We need to put a team in place but for the next five years," he said. "I want a team that has the energy, the ideas and the enthusiasm to take this state forward."