Welsh Assembly: Elin Jones says no extra AMs until 2021
A decision on whether to have more assembly members has been put off until after 2021.
There were proposals to add another 20 or 30 AMs to the current 60 before the next elections in two years' time.
But Labour has said it will not back the plan or changes to the way AMs are elected without first putting it to voters in a manifesto.
Presiding Officer Elin Jones today confirmed it would not be possible to change the law before the election.
However she said "we are confident that the case in favour of increasing the number of AMs has been made".
She set out the next steps in plans to reform the assembly in a letter to AMs.
Although she did not name Labour, the party said at its Welsh conference in April that legislation to change the size of the assembly and the electoral system should not happen "without a public mandate via a manifesto commitment".
That effectively killed off any prospect of making the changes before 2021 and made it unlikely that the number of AMs will rise above 60 until the following election in 2026.
The assembly is in the process of changing its name to the Senedd and lowering the voting age to 16.
As part of a second phase of reform, it will look at other proposals published by a panel of experts in 2017.
Led by Cardiff University's Professor Laura McAllister, the panel concluded that more AMs were needed to keep pace with the assembly's growing powers and responsibilities.
It said: "Calling for more politicians is unpopular, but our analysis of the evidence demonstrates that all the alternatives to an increase in size have been tried and tested without adequately addressing the capacity gap we have identified."
In her letter to AMs, Ms Jones says: "As the challenges facing the assembly's capacity intensify, we are confident that the case in favour of increasing the number of AMs has been made.
"Nevertheless, the issue of reforming the electoral system continues to spark a wide range of views, with one party having already confirmed that it would require a manifesto commitment before any such change was implemented.
"On this basis, the commission has decided it is not possible to legislate on Phase 2 of electoral reform in this Assembly.
"However, our work to explore issues relating to the size of the assembly and how members should be elected will continue assisting the public debate and political parties as they consider their views on these matters."