Increase number of AMs from 60 to 100, says report
The number of AMs in the Welsh assembly needs to be increased from 60 to 100 in order for them to properly scrutinise the government, a report has said.
The Electoral Reform Society and the UK's Changing Union project researched the assembly's size.
They found it had a much smaller number of AMs compared to similar law-making bodies around the world.
The Welsh government said it would be premature to speculate ahead of a decision on extra assembly powers.
The Scottish Parliament has 129 members, while Northern Ireland's Assembly has 108.
The report, Size Matters - Making the National Assembly more effective, says the backbench AMs are badly overstretched and are struggling to effectively scrutinise a "powerful and well-resourced" government.
It is not the first time the number of AMs has been questioned.
In 2004, the Richard Commission, which looked at expanding the assembly's powers, recommended 80 AMs once it received law-making powers.
Those recommendations were not implemented.
The Silk Commission, set up by the UK government, is currently looking at the devolution settlement in Wales and has already said ministers in Cardiff should be given the power to vary some tax rates.
The new report found 80 was "an arbitrary number", and said after an international comparison of similar bodies, the number of AMs should be 100.
An assembly expanded to this size would cost taxpayers about £10.1m per year, but the report's authors argued that with the number of MPs and local councillors both likely to be reduced, it was time for a "mature debate" about the balance of political representation.
Presiding officer Rosemary Butler has previously called for the number of AMs to increase, but the Welsh government said at the time there was "no appetite" among the public for more politicians.
Deputy presiding officer David Melding AM said: "I welcome this report which has, for the first time, provided us with some relevant international comparisons and analysis of the demands on assembly members.
"I am sure this report will play an important role in informing the current debate as we move towards the publication of the Silk Commission's inquiry."
Steve Brooks, director of the Electoral Reform Society in Wales, said: "As more and more powers are added to the assembly, AMs are buckling under the weight of devolution."
Chair of the UK's Changing Union project, Professor Richard Wyn Jones, said: "Few, if any serious observers would argue that just over 40 backbench assembly members is enough to do the job effectively.
"Indeed the evidence clearly shows that even without the additional financial powers already recommended by the Silk Commission, the National Assembly is overstretched."
A Welsh government spokesperson said: "It would be premature for us to speculate on what any additional powers might mean for the size of the National Assembly, given we do not yet know what the Silk Commission will recommend."
The Welsh Conservatives said: "Job creation for politicians would rightly be questioned by the public at what remains a challenging time for the Welsh economy.
"What is urgently needed is more scrutiny of legislation, better engagement with the public and more topical and extensive assembly proceedings."
Plaid Cymru AM Simon Thomas said with the prospect of financial and taxation powers becoming more real, there was a need to ensure that the assembly was able to "meet the increased demands".
Eluned Parrott AM said the Lib Dems supported a rise to 80 AMs.
"While I understand that increasing the number of politicians is never going to be popular, it's right that we should have an open and honest debate about the issue," she said, adding the people of Wales would get more capacity to scrutinise with additional AMs.