By Tom Fairless

The head of Germany's Bundesbank, Jens Weidmann, launched a fresh attack on the European Central Bank's EUR2.3 trillion bond-purchase program on Thursday, a week after the ECB pledged to continue the initiative through the end of this year.

Speaking to an audience of economic experts in Berlin, Mr. Weidmann warned that the so-called quantitative-easing program had created economic distortions and said the ECB should exit its easy-money policies as soon as inflation rises in a sustainable way.

"Central banks shouldn't become the prisoners of markets or fiscal policy," Mr. Weidmann said. Government bond purchases "carry precisely this risk," he said.

The Bundesbank chief has long been skeptical of the ECB's bond purchases. But his latest comments come amid a burst of criticism of ECB policy in Germany, Europe's largest economy, where a surge in inflation has sparked fears about the impact on the nation's savers. Politicians and economists have been lining up to call on Frankfurt to reverse course.

Sabine Lautenschläger, a German who sits on the ECB's six-member executive board, p lunged into the debate on Tuesday, saying she hoped the central bank could "soon turn to the question of an exit" from easy-money policies.

It was the first time that an ECB board member has indicated that the days of QE may be numbered. Only last week, ECB President Mario Draghi said the issue of tapering, or winding down, the bank's controversial stimulus program hadn't even been discussed by policy makers.

Outside Germany, the ECB's bond purchases still have broad support. The bank's 25-member governing council agreed last month to extend the program by nine months, or a half-trillion euros, through the end of December.

The head of France's central bank, François Villeroy de Galhau, defended the ECB's policies in a speech in southern Germany earlier Thursday. He stressed that the ECB hasn't discussed any exit strategy, and that its recent policy decisions had "given predictability for the whole year to come."

Mr. Weidmann acknowledged that the ECB's easy-money policies were still appropriate because inflation remains weak, and its recent increase was driven largely by energy prices.

But he stressed that the economic outlook for the currency union was "quite positive" and said inflation was expected to gradually approach the ECB's target of just below 2%.

"When this price development is sustainable, the conditions for an exit from easy-money policies have been achieved," he said.

He warned that the long period of lowinterest rates had created adverse side effects, including a squeeze on the profits of banks and insurance companies, as well as potential asset-price bubbles.

Crucially, the QE program makes government debts appear more sustainable than they are, he argued. Governments currently are saving about EUR250 billion a year in interest payments, compared with the rates they would have paid prior to 2007, he said.

Mr. Draghi has defended QE by arguing that the ECB isn't doing anything different from other major central banks, who all have launched similar bond-purchase programs.

But Mr. Weidmann disputed that. He said the ECB's bond purchases differed substantially from those of the Federal Reserve because the Fed bought federal debt, and not the debt of individual U.S. states.

The Bundesbank chief also used his speech to warn against a global turn toward economic protectionism. That appears increasingly possible following the election of U.S. President Donald Trump, who has pledged to pull out of international trade agreements and put "America First."

"We must counter the increasing tendency toward separation and nationalism with intelligence, and not give in to the logic of trade wars" Mr. Weidmann said.

--Todd Buell in Munich contributed to this article.

Write to Tom Fairless at tom.fairless@wsj.com

(END) Dow Jones Newswires

January 26, 2017 14:14 ET (19:14 GMT)

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