Former Treasury secretary Ken Henry says Treasurer Jim Chalmers’ use of the department to reveal the potential cost of the Coalition’s tax breaks for business lunches is unfortunate but forms part of a long-standing practice of governments leaning on public servants that has been occurring since the 1980s.

Dr Henry weighed in after shadow treasurer Angus Taylor complained Dr Chalmers had weaponised Treasury to estimate that exempting small businesses from fringe benefits tax for $20,000 of meal and entertainment expenses could cost between $1.6 billion and $10 billion. The Coalition says the Parliamentary Budget Office estimates the two-year cost would be less than $250 million.