Six of Plaid Cymru's 15 assembly members say they will refuse to take an inflation-busting 8.3% pay rise.
Conservatives accused the AMs of political "posturing". Other Plaid AMs are considering their position.
Meanwhile, the chairman of the independent panel which recommended the rise said it reflected increased workloads and responsibilities.
AMs will see salaries rise to £50,692 a year, to bring them closer to the amount earned by MPs at Westminster.
The recommendation will see AMs' pay rise to 82% of an MPs' salary.
The cross-party Assembly Commission, which sets pay, insisted the rises were an inevitable result of the assembly's enhanced powers to draft and pass laws.
Sir Michael Wheeler-Booth, who chaired the independent panel, said the principal reason for recommending the rise was that AMs were doing a new kind of job since the Government of Wales Act 2006.
"They are having to look at primary legislation for the first time," he said.
"That shows that Welsh assembly members are doing a bigger job with increased responsibility and complexity, more committees."
The Welsh assembly's expenses and allowances system was inherited from Parliament and it was time for a "fundamental review of the whole thing", he said.
Six of Plaid Cymru 15 AMs - Chris Franks, Alun Ffred Jones, Leanne Wood, Nerys Evans, Bethan Jenkins and Dai Lloyd - have already said they will not take the pay rise.
Ms Wood said people would find it difficult to understand why AMs had been given such a large increase when public sector workers have had to accept a 1.9% deal.
"If money is tight it should be tight for all of us and that is why Plaid Cymru members felt we were unable to support the increase," she said.
"I accept that the work load has increased but what we cannot accept is that this is good timing when everybody else has been asked to tighten their belts."
UK: Westminster MPs earn £61,820
Scotland: MSPs earn £53,091 (86% of MPs salary)
Wales: Recommendation that AMs will earn £50,692 (82%, up from 76%)
Northern Ireland: MLA pay being reviewed, could rise to £52,000 (84%)
The Welsh Conservatives challenged Plaid AMs to say whether or not they would accept the new pay deal.
Tory assembly leader Nick Bourne AM said they were displaying "the worst kind of political opportunism".
He said: "The people of Wales will see through this posturing.
"Plaid AMs need to make it crystal clear now whether or not they will accept the pay increase agreed because of the assembly's new responsibilities and powers."
Lord Elis-Thomas, who is the assembly's presiding officer and chair of the commission, said there was a "price to pay for effective democracy".
He said: "I think AMs are working hard and are overseeing, not only our own budget of £45m for the Assembly Commission for all democratic services but also the £16bn spend of Welsh Government.
"That's the price of an effective democracy."
A Welsh Labour spokesman said they would abide by the decision of the commission, as did the Welsh Liberal Democrat assembly group, which said it was "intended to reflect the changes in the balance between the responsibilities of AMs and MPs".
AMs are also set to receive this 1.9% below inflation rise, bringing a back-bench AM's salary up to just over £50,000 a year.