Labor has written to the chair of the House of Representatives economics committee demanding to know how the dates of the inquiry into the nation's major banks were decided.
It certainly wasn't due to any input from non-government members of the committee, Labor's financial services spokeswoman Katy Gallagher says.
The government announced on Thursday that October 4-6 has been set aside for the bosses of ANZ Bank, Commonwealth Bank, National Australia Bank and Westpac to be grilled by the committee - the government's answer to opposition parties calling for a royal commission.
Senator Gallagher has written to the chair of the committee, Liberal MP David Coleman, concerned the banks were consulted on the dates long before the committee was told.
"Labor understands that discussions with the banks have been underway since at least the beginning of September," Senator Gallagher says in a copy of the letter obtained by AAP.
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She says a rushed 15-minute meeting was held on Thursday to rubber stamp the dates.
Among her concerns, the senator is worried the hearing dates fall within a period for several of the banks between the close of their financial year and the reporting of their final results to the Australian Stock Exchange.
"This may significantly restrict the amount of public commentary their representatives can provide," the senators says.
She says if the public is to have any confidence in this inquiry process, it is important it is seen as impartial.
Opposition Leader Bill Shorten went further, saying the process has been a "stitch-up from the start".
"This is further proof that Malcolm Turnbull will bend over backwards for the big banks. He is the best friend the big banks have ever had," he told AAP.
CBA is due to face the committee on October 4, ANZ on October 5, and NAB and Westpac on October 6.
Mr Coleman said it was standard practice for the committee secretariat to discuss potential dates and times with witnesses before committee members decided when hearings would be held.
"The criticism by Labor of the hearing dates is ludicrous," he said in a statement.
The secretariat had spoken about scheduling with the major banks, the Reserve Bank and regulatory authorities "in recent weeks" and would continue to do so, he said.
