Opposition Leader Jeremy Hanson on Wednesday morning presented a bill to allow the government to add members to its ministry, upping the ante in an ongoing debate over ministerial workload.

It followed the opposition's refusal last week to support the government's bid for an overall expansion of the number of members in the Assembly, suggesting instead that public opinion be sought on the issue. Its refusal prompted the Chief Minister to warn that future governments would be forced to consider assigning some ministerial duties to non-elected officials.

An expert reference group had recommended that the Assembly be enlarged over time, more than doubling from 17 to 35 MLAs.

Greens MLA Shane Rattenbury said the idea of a sixth minister should be considered in the context of expanding the Legislative Assembly as a whole.

''I think [Mr Hanson] is seeking to hold the debate hostage, and we need to have a more mature approach where we consider these issues together,'' he said.

ACT Chief Minister Katy Gallagher said while she welcomed Mr Hanson's ''admission that he accepted very publicly that ministers' workloads are onerous'', she would commit only to considering the bill.

She agreed with Mr Rattenbury that the overall size of the Assembly should be considered. ''What we have is four members on the backbench, but they are all carrying between three and five committees each. If you take someone out of that, we immediately ask three members to start taking on four and five and six committees.''

Mr Hanson said if one member of the government, rather than two, sat on assembly committees it would halve their workload overnight.

And if fewer government members sat on committees it would free time for one of them to take up a sixth ministry, he said.

‘‘I really am confounded by what’s happening here, why the chief minister is so resistant to appoint one of her back bench to the ministry,’’ he said.

“What we have is four members on the back bench, but they are all carrying anywhere between three and five committees each. If you take someone out of that, we immediately ask three members to start taking on four and five and six committees. That becomes unreasonable,” she said.

The chief minister accused Mr Hanson of playing politics with the debate.

“I think the issue of the size of the assembly has to be part of the discussion,’’ she said.