An attempt to prove that France's first lady, Valerie Trierweiler, is a burden on the state has backfired after it emerged that her predecessor Carla Bruni cost taxpayers three times as much.

Guillaume Larrivé, an MP with the former president Nicolas Sarkozy's UMP party, tabled a parliamentary question in March asking how much Trierweiler's staff at the Elysée palace cost.

The answer came this week in France's official journal, which stated that the five people working for President François Hollande's unmarried partner cost a net total of €19,742 (£16,600) a month.

Larrivé did not ask for information about Bruni, the supermodel turned pop star who became Sarkozy's third wife months after his election victory in 2007. But officials from Hollande's Socialist government said that to put Trierweiler's costs into perspective they should be compared with those of her predecessor.

They revealed that Bruni, now 45, had eight people working for her at the Elysée at a monthly cost of €36,448. Bruni also outsourced the administration of her website, which added a further €25,714 for two people's wages to the bill, bringing the total to €60,000 a month.

That was more than three times the cost of the team working on humanitarian and charity projects for Trierweiler, 48, a twice-divorced political journalist.

Trierweiler has not publicly commented on the affair, but it will come as a boost to a first lady who has struggled to endear herself to voters. A year after her partner's election, opinion polls suggest up to two-thirds of the French have a negative opinion of her – although she is not quite as unloved as Hollande, who polls say is the least popular French president in decades.

The first lady's lower budget chimes well with Hollande's efforts to show the public that his government, which is implementing harsh spending cuts across the board, is ready to practise what it preaches. Within days of coming to power last year, Hollande cut his own and his ministers' pay by 30%.

This week it was announced that more than 1,000 bottles of wine from the French presidential cellar are to be auctioned off, with the proceeds to be reinvested in more modest vintages and the excess returned to state coffers.