By Harry Wilson
The unprecedented step saw the euro sink to a four-year low after Germany said that from midnight shorting of credit default swaps of any European government would be banned. The prohibition is an attempt to counter speculators that Berlin believes are trying to destabilise the region's sovereign bond market.
Traders greeted the move by BaFin, the German regulator, with a mixture of anger and astonishment. One bond trader said he expected Wednesday's trading session to be one of the most volatile in living memory: "It will be complete chaos, I really don't know what the Germans think they are doing."
One immediate effect was that the cost of insuring European government debt fell as markets were hit by a so-called "short squeeze" where investors with short positions are forced to offload their holdings and buy the bonds, causing the price to increase.
This is certain to please the German authorities, who have waged an increasingly hostile war of words with supposed speculators.
BaFin said the ban was being introduced due to "extraordinary volatility in debt securities issued by eurozone countries".
In a statement, it said short-selling had led to excessive price movements "which could have led to significant disadvantages for financial markets and have threatened the stability of the entire financial system". However, traders said that the measures, which will also prohibit the naked short-selling of shares in major German financial institutions, such as Allianz. Commerzbank, and Deutsche Bank, could lead to an immediate backlash from investors around the world.
They added that the ban was likely to be effectively unenforceable. It will not stop traders from shorting the bonds and shares using other European markets.