Labor has enlisted the public service to take down another tax break from the opposition, as Treasury warns that a proposed deduction for charitable food donations could allow companies to pocket millions of taxpayer dollars for gifts already being made.

Shadow treasurer Angus Taylor has accused Treasurer Jim Chalmers of weaponising the public service after the government asked Treasury to estimate the cost of the Coalition’s proposal to introduce a $20,000 annual tax break for small business meal and entertainment expenses.