There are currently five ministers on the government front bench, including Greens MLA Shane Rattenbury, and eight Labor members in the 17 MLA Assembly.

Chief Minister Katy Gallagher told the Assembly on Thursday morning "it was time to act" to increase the number of government ministers, but the bill also looked "many years into the future" by allowing for up to nine.

Ms Gallagher said the Assembly would also have to consider whether the ministry could be increased without increasing the number of MLAs from the current 17.

"More Assembly members would allow for greater diversity or specialisation, more manageable workloads, high quality committee work and stronger, more responsive governance overall," she said.

"The current workload of ministers is significant.

"With 25 portfolios, spread across five ministers, keeping abreast of day-to-day matters, being responsive to both community members and the media, prioritising emerging issues that need our immediate attention, is a considerable task."

Liberal Leader Jeremy Hanson had already proposed that the government be permitted to appoint one extra minister.

Ms Gallagher wants to increase the size of the Assembly to at least 25 members but would need the support of the opposition to do so. Changes to the size of the Assembly can only occur if a two thirds majority of MLAs vote in favour.

Ginninderra MLA Chris Bourke was previously a minister, but lost the position when Labor offered Mr Rattenbury a seat in Cabinet in return for his support to form government after last year's election.

The bill is expected to be debated next month.