James Evans says the Welsh Government should be spending money on helping people in need rather than planning to reform the Senedd at a cost of hundreds of thousands of pounds.
The Brecon and Radnorshire MS asked Counsel General Mick Antoniw about the likely cost of enlarging the Senedd.
He said First Minister, Mark Drakeford, had said it was intended that the legislation would allow the Government to have up to 19 ministers.
Mr Evans said: “If they were full ministers with senior special advisors, it would cost £869,000.
“If they were deputy ministers with standard special advisors, it would be £645,000.”
He told Mr Antoniw that the public watching Senedd proceedings would much prefer that money be spent on people in need who are struggling rather than putting ministers behind desks in Cathays Park.
Mr Antoniw said preparation and delivery of Senedd reform legislation requires expenditure that is allocated in the 2023-24 budget.
He told Mr Evans: “Detailed estimates of the financial implications of Senedd reform will be published alongside the Bill on introduction for scrutiny by Members during the Bill's passage.”
Speaking after the Senedd session, Mr Evans said: “I am sure that many people would rather see this money spent on vital public services and to those in need, not creating more politicians in Cardiff Bay.
"I and my Welsh Conservative colleagues are calling for a referendum on plans to expand the number of politicians in the Welsh Parliament."