Delegates at this weekend's Labor state conference voted to ban offering cabinet positions or ministerial portfolios to non-ALP politicians in the event of future hung parliaments.

The Parliamentary Labor Party must also now secure support of the broader ALP membership before forming minority government.

The changes follow an internal inquiry into the party's thumping state election loss, which found a power-sharing arrangement struck between Labor and the Greens in 2010 had turned traditional ALP supporters away from the party.

Opposition Leader Bryan Green said yesterday the rule changes would sever a perceived connection between the two parties.

However, Deputy Premier Jeremy Rockliff said the changes ``[left] the door wide open'' for another Labor-Greens deal.

``We have seen it all before when Labor went to an election saying there would be no deal with the Greens and then, against the clear wishes and best interests of Tasmanians, did one anyway,'' Mr Rockliff said.

``Labor remains wedded to the Greens in Tasmania and nationally, and Bryan Green is doing nothing to change that,'' he said.

Greens leader Kim Booth said Labor's reforms were a cynical ploy to avoid responsibility for joining the Liberals in slashing House of Assembly numbers in 1998.

Mr Booth said returning to a 35-seat lower house would negate the need to fill future minority government cabinets with crossbench politicians.

He called on his political opponents to support restoring lower house numbers.

However, neither party appears likely to support the push.

Mr Booth said some form of power-sharing Parliament was likely to follow the next state election, and the Greens were prepared to work co-operatively and transparently in future multi-party governments.