The cost of education for diplomats' children has grown by more than a third in two years and reached nearly $20 million in 2016, new figures from the foreign affairs department reveal.
Numbers released under freedom of information rules show schooling allowances for its staff grew from $14 million in 2014-15 to $18.8 million last year as parents working for the Department of Foreign Affairs and Trade used the children's education subsidy.
The department said it paid for the schooling to give children of staff an Australian-level equivalent education while their parents were working overseas.
But it also pays school fees for dependent children who remain in Australia while their parents are posted in other countries. Children of departmental staff posted overseas numbered 787 last year.
"DFAT is committed to deploying a diverse range of officers overseas, and this includes families with children," a spokeswoman said.
"Dependent children of government officers on long-term posting should be able to access education that is equivalent to that received in Australia."
DFAT did not answer a question asking the cause of the nearly $5 million increase in spending between 2014-15 and last year, however it said exchange rate variations influenced costs.
Spending on the allowance grew 21 per cent in 2015-16 to $17 million, before climbing by 10 per cent the following year.
DFAT staff stop receiving education subsidies when their child finishes full-time secondary education, or at the end of their posting.
There is no assistance for tertiary education, and the allowance is also limited to the cost of compulsory tuition fees. All other costs are at staff expense.
The allowance was one of multiple benefits and perks brought under scrutiny by a 2016 review prompted after DFAT spent an estimated $215,000 or more sending nearly two dozen senior bureaucrats from Canberra to Paris to attend an inhouse talkfest about ways to save money.
Following the review, diplomats lost long-standing allowances for cable television, financial advice and outfits in a crackdown on entitlements expected to save the government $37 million, but the education allowance remained.
DFAT officials said in May the agency would shoulder more than half the savings burden for the Coalition's measure to bring allowances in line with "community expectations".
Diplomats serving in less dangerous cities also lost a hardship allowance graded by the liveability of their location, while the government said it would apply limits to a cost of posting allowance expected to provide a bulk of the savings.