France’s new prime minister said Wednesday that the country’s finances were in critical condition, as signs mounted that the government faced an uphill battle to control a ballooning debt and deficit that have become among the highest in Europe.

“I am discovering that the country’s budgetary situation is very serious,” said Michel Barnier, who was appointed by President Emmanuel Macron this month after a summer in which France hobbled along effectively without a government. Mr. Barnier told the Agence France-Presse news agency that the budget hole required immediate and responsible action.

The warning came as the head of the Court of Auditors, the supreme body for auditing government spending, told Parliament on Wednesday that the country would miss a target to lower its deficit this year, and would have to find ways to come up with an eye-popping 110 billion euros in savings in the next several years to comply with E.U. budgetary rules.

The governor of the French central bank, Francois Villeroy de Galhau, added that the country would need to plug three-quarters of the deficit with spending cuts and the rest with new tax increases — something that Mr. Macron had promised not to do.

“We have too much debt, too much deficit,” Mr. Villeroy de Galhau said in an interview on French television Wednesday.

France’s debt load has ballooned to €3 trillion, or more than 110 percent of gross domestic product, the highest in Europe after Greece’s and Italy’s. The deficit stands at €154 billion, representing 5.5 percent of economic output, the worst performance after Italy’s, and well above the bloc’s 3 percent limit. Around €80 billion a year goes toward paying interest on the debt.