A leading German conservative levelled sharp criticism at the European Central Bank on Sunday, describing further purchases of euro zone sovereign debt by the bank as toxic.

Alexander Dobrindt, deputy leader of the Christian Social Union (CSU), told Die Welt newspaper that he rejected continued intervention by the ECB on debt markets to push down borrowing costs for debt-saddled states.

I find it dubious that the (ECB) is always buying new sovereign bonds from indebted states, Dobrindt said in comments to be published on Monday.

He who covers himself with rotting paper eventually ends up with a toxic shock, said Dobrindt, whose party is the Bavarian variant of Chancellor Angela Merkel's Christian Democrats and one of three in her centre-right coalition.

The ECB has reluctantly carried out its bond-buying program since 2010, totalling some 187 billion euros so far. But it has shown little sign of shifting into a higher gear even as countries like Italy risk being shut out of commercial markets.

The bank's policymakers have rejected international calls to intervene decisively to shore up the euro zone, but recent volatility in regional debt markets has made a decision on a bigger role for the monetary authority more pressing.

In his first news conference as the new ECB president earlier this month, Mario Draghi offered no commitment to scale up the bank's bond-buying, instead describing it as limited.

In comments to Die Welt, Dobrindt took issue with this, accusing Draghi of stepping up the programme: in a highly problematic debut, he drastically accelerated purchases of debt from crisis states, he said.

We would never have agreed to a European Central Bank if we had suspected it would one day be run Italian-style, he said, referring to German fears of loose monetary policy leading to spiralling inflation.

Dobrindt also underlined his support for higher voting rights for Germany in the ECB, saying it was unfair that Germany bear almost 30 percent of the financial responsibility but have only the same weight as other euro countries.

(Writing by Brian Rohan; Editing by Elaine Hardcastle)