Senior ministers told Commission Chairman Tony Shepherd last year that any more cuts, beyond the 14500 often cited by the Coalition, were to be made "responsibly" and based on "effective staffing."

The letter from Treasurer Joe Hockey and Finance Minister Mathias Cormann was sent in November after the Coalition walked away from its pledge to cut 12,000 jobs, claiming spending cut by the previous Labor government would see 14,500 positions lost.

But the ministers did not forbid Mr Shepherd's commission from pursuing even more job cuts to the bureaucracy, if it believed they were necessary.

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In their letter, tabled during the commission's appearance before a senate committee on Wednesday, Mr Hockey and Mr Cormann accused their predecessors of making untargeted cuts.

"These reductions were largely untargeted, making no distinction between higher or lower priority areas of spending and having no regard to the financial health of different parts of government," the ministers wrote.

"In contrast, our government will ensure that any staffing reductions we implement will match the reforms we make to the size and shape of government flowing from the government's consideration of the Commission's work."

Mr Hockey said he wanted any job cut recommendations from the commission to be linked to more efficiencies.

"I request that all of the commission's proposed reforms are based on effective staffing and that these are linked to efficient services," Mr Hockey wrote.

"The government's approach is that the public sector reductions must be done responsibly through deliberate choices about priority areas, the proper function of government and the opportunities to reform the way we deliver services."