Despite Jones’ recent deferral of the determination’s start date to next year, the industry's concerns have failed to abate due to his refusal to modify the substance of the changes.

The Coalition, siding with practitioners and professional bodies, will bring the controversy to a head on 10 September through a disallowance motion by Liberal senator Dean Smith.

After a party room meeting, top Liberal MPs released a joint statement on Tuesday outlining what they believed were key flaws with the determination, tabled in Parliament on Monday.

These included the “rushed” drafting without consultation and regulator guidance, as well as the retrospective application of client disclosure requirements and the rules’ disproportionate impact on small practices and sole practitioners.

“Labor is layering red tape upon red tape on finance professionals that just drive up costs for consumers,” shadow treasurer Angus Taylor said.

With a majority vote needed for the disallowance motion to succeed, Smith said the Opposition would be rallying crossbenchers for support.

“The Coalition calls on all crossbench senators to support the disallowance and reverse the regulatory burden and uncertainties that will fall on accountants, bookkeepers, and other financial professionals at a time when they can least afford it,” he said.

Independent senator David Pocock has hinted at the possibility of voting in favour of the motion, as reported by International Tax Review.

But the position of the Greens, who hold the balance of power in the Senate, remains unclear.

The TPB reform package that included the insertion of section 30-12 of the Tax Agent Services Act (TASA) to give the Assistant Treasurer the power to unilaterally modify the code was welcomed by Senator Barbara Pocock in a media release at the end of last year.

More recently, however, lower house MP Max Chandler-Mather wrote to Jones backing up practitioner’s concerns over the determination, calling on the government to provide clarity on the “vague and contradictory” rules.

Jones has maintained the obligations are “modest” and that the tax industry was consulted throughout the development of the code changes.

But the joint bodies have disputed this claim and say the concerns they raised in the original exposure draft were ignored.

"These code changes cannot be described as ‘modest’,” Matthew Addison, co-chair of the TPB’s Tax Practitioner Governance and Standards Forum, said on behalf of the bodies on Wednesday.

“They are sweeping, disproportionate to legitimate concerns of misconduct, and have left practitioners uncertain, confused and overwhelmed about their new obligations.”