A Senedd committee are calling for between 80 and 90 Members of the Welsh Parliament to sit in the chamber for the 2026 election.
They say the evidence is "clear and compelling" that there are too few of them at present. Currently there are 60 Members of the Senedd.
Last year, the Senedd decided that more members were needed, but that further work was required to consider how that could be achieved. The Senedd Electoral Reform Committee looked at the recommendations of an expert panel, which originally called for the increase in 2017.
The committee has Labour and Plaid Cymru members but the Conservatives refused to join it and the Brexit Party later withdrew.
It is chaired by the Labour MS for Merthyr Tydfil and Rhymney, Dawn Bowden, and the group has decided that MSs are under "too much time pressure" because their responsibilities have greatly increased since devolution began in 1999.
“Devolution has been an exciting journey, and the Senedd we have today looks radically different from how it did when it was established over 20 years ago", she said.
"With expanded powers and responsibilities, it now makes decisions on laws that affect every aspect of peoples’ lives and has responsibility for setting some tax rates.
“We believe that the people of Wales would be better served by a Senedd which has the right number of Members. A larger Senedd would be cost effective, as Members would be better able to hold the Welsh Government to account for its spending and decisions, and pass better legislation, as well as helping people across Wales with their problems".
Next year's election will go ahead under the existing system, but the political parties are expected to put pledges into their manifestos about changes to the number of MSs and how they are elected.
However, the Conservative leader in the Senedd, Paul Davies, has made it clear that he favours no change.
"This is a report which represents the views of just two parties in the Welsh Parliament and currently there is no public appetite for an increase in the number of politicians", he said.
"The current voting system enables a roughly proportional Senedd while maintaining local accountability with two thirds of Members of the Welsh Parliament elected on a first past the post basis; we see no reason to change it."
The Plaid Cymru leader, Adam Price, was much more enthusiastic.
"At a time when devolution is under direct assault from Westminster we need now more than ever before a strengthened Senedd", he said.
"Better value for money than any five billion pound refurbishment to Westminster, Plaid Cymru has long maintained that our national parliament needs more powers and that our electoral system needs urgent reform."
If the committee gets its way, the enlarged Senedd would be elected five years later using multi-member constituencies and the Single Transferable Vote (STV) proportional voting system.