Rosemary Butler calls for AM numbers to rise from 60 to 80
The number of AMs at the Welsh Assembly must increase from 60 to 80 otherwise "the strain will begin to tell", its presiding officer has said.
Dame Rosemary Butler said only 42 members were available to sit on a "relentless cycle" of committees.
She was giving evidence to MPs on the Welsh Affairs Committee, who were sitting in Cardiff on Monday.
Meanwhile, First Minister Carwyn Jones told the committee Wales needed a "fairer funding" system.
The committee of MPs was gathering evidence on the Draft Wales Bill from Dame Butler, Mr Jones, Finance Minister Jane Hutt and finance committee chair Jocelyn Davies.
Dame Butler claimed the MPs would be "amazed" at the work being done by assembly members.
She said the assembly had 60 members but, as government ministers and certain other office holders did not sit on committees, only 42 AMs were available to sit on scrutiny committees.
Without a second chamber - such as the House of Lords, which considers legislation after it has passed through the House of Commons - the Welsh Assembly has to get legislation "right the first time", she added.
She said AMs did not have the "luxury" to specialise, as MPs do in Westminster, because they are on a "relentless cycle" of committee meetings.
Responding to claims the public would not warm to the idea of further politicians, she said: "People have to understand, if we want to deliver quality legislation we need the best possible people."
She added: "It's a big educational project. People need to see that politicians are essential."
Mr Jones was also asked about the number of AMs necessary to scrutinise legislation. He said the current workload for backbenchers was "enormous".
He added: "We can manage with 60, but 80 would be ideal."
Mr Jones repeated his call for what he calls fairer funding for Wales.
He claims the current model of funding for Wales, the Barnett Formula, short changes Wales to the tune of hundreds of millions of pounds a year.
He opposes holding a referendum on income tax unless the UK Treasury changes the way it sets the Welsh government's budget.
Otherwise, the proposed powers would be a "strait jacket" he said.
He told the MPs: "The immediate issue is fairer funding.
"When that is addressed we can look at how fiscal devolution can work in the future."
When asked whether a referendum on tax-varying powers for the assembly was likely by 2017, as has previously been suggested, Mr Jones said it was "an ambitious target" and "matters in Scotland need to be addressed first".
The first minister also suggested the borrowing ceiling of £500m proposed in the draft Wales Bill was too low, and "should be closer to a billion".
Finance Minister Jane Hutt said it would be "helpful" if the Welsh government could issue its own bonds.