Tasmanian MPs have found a historic decision to cut the size of the state's parliament has undermined government accountability, recommending the Lower House be boosted by an extra 10 politicians.

Key points: Tasmania's House of Assembly was reduced in size from 35 to 25 MPs in 1998

Tasmania's House of Assembly was reduced in size from 35 to 25 MPs in 1998 A report by a committee of Greens, Liberal and Labor MPs says that damaged the state's democracy

A report by a committee of Greens, Liberal and Labor MPs says that damaged the state's democracy The report says too many decisions are left to unelected advisors, and it is difficult for MPs to effectively represent their electorates

A report into the 1998 decision to reduce the House of Assembly from 35 to 25 members found there were now too many ministerial advisers making decisions without direct accountability to the people of Tasmania.

It also made it difficult for opposition parties to effectively scrutinise the government, for any politician to effectively represent their electorate, and created "challenges" when people vacated government and needed replacement, the report said.

The Lower House committee — made up of Green, Liberal and Labor MPs — unanimously recommended the restoration of parliament.

"The Committee specifically notes senior political figures and former members of parliament from across the political spectrum agree it was a mistake to reduce the numbers in the House of Assembly," the report said.

The inquiry looked at a 2018 Greens bill that would have the House of Assembly restored to 35 members.

The report noted that while there would be a financial cost to restoring the numbers, the cost to democracy and good governance of not having an effective parliament was significantly greater.

Committee 'united' in boosting MPs

Committee chair and Greens leader Cassy O'Connor said every member of the committee was united in recommending the numbers be restored.

"In a rare display of political unity, every member of that committee, Liberal, Labor and Greens, agreed that the numbers in the House of Assembly should be restored to 35 in the interests of good governance and Tasmania's democracy," she said.

Liberal member for Clark Sue Hickey said the report was one of the most significant to be handed down in recent years.

"The only way to give Tasmanians better government is to increase the numbers of people in the parliament, and to enhance the skill set," she said.

"I do hope this Parliament in 2020 has the political courage to be able to support this for the people of Tasmania."

The size of Tasmania's Parliament was cut from 35 to 25 in 1998. ( Supplied: Parliament of Tasmania )

Business backs bigger Upper House

The Tasmanian Chamber of Commerce and Industry's Michael Bailey added his voice to the chorus of support for adding 10 more politicians to the Lower House.

"It's critical that we rectify this, it's critical that we restore parliament to the 35 numbers that we had back in the 90s," he said.

"We know all parliamentarians say this is important behind the scenes, now it's important to step up and make sure it happens."

The report also recommends a new joint parliamentary inquiry be set up to look at establishing dedicated seats for Tasmania's Aboriginal people.

Ms O'Connor said while the bill to restore the numbers was not the right mechanism to address the lack of Indigenous representation in the state's parliament, it was a moral wrong that needed to be remedied.

"We recognise that that would make a huge difference to reconciliation and to the capacity of Tasmania's Aboriginal people to advocate for their future, and for a better deal for their people."

'Not a current priority': Deputy Premier

Deputy Premier Jeremy Rockliff said he hadn't read the report but didn't view increasing MPs in the Lower House as a priority.

The Braddon MP holds six portfolios and said he wasn't overworked, and believed Parliament was operating effectively.

"Our consistent position is it's not a current priority for the Government," he said.

"There are many needs within our community such as health and education, and community safety, so it's not a priority of ours at the current time.

"We'll no doubt read the report with great interest. But it's not a priority."