The Swiss government has unveiled a bill designed to accelerate the return of assets locked in Swiss accounts to the countries they were looted from, amending legislation after a series of embarrassments in recent years, a report from Reuters said.

A loophole in the system meant the Swiss repeatedly failed to confiscate and hand over to Haiti, one of the world's poorest countries which suffered a devastating earthquake in January, nearly $6 million belonging to former ruler "Baby Doc" Duvalier held in Switzerland, the news service said.

The report highlights how Switzerland, which has seen its centuries-old tradition of bank secrecy come under attack from countries seeking to chase tax evaders, is attempting to show it is willing to co-operate over the return of assets deposited in its accounts under suspicious circumstances. In the past, banks have been in the firing line for holding assets once seized from Jewish families by the Nazi regime in Germany.

Under the old rules, the Swiss cannot return assets unless the country of origin files a formal request for assistance in criminal matters.

"Experience has shown that this system reaches its limits when the failure of national legal systems means that countries are unable to carry out national criminal proceedings," the Foreign Ministry was reported saying in a statement.

Many former authoritarian rulers of mostly emerging countries stashed fortunes in Swiss bank accounts, for years hiding behind the country's secrecy laws.

Switzerland, which no longer accepts such illicit assets and has introduced strict money-laundering rules, has returned to countries over the past 15 years more than SFr1.7 billion Swiss francs that once belonged to corrupt politicians.

This included assets from Nigeria's ex-ruler Sani Abacha, former Philippine's president Ferdinand Marcos and the former head of Peru's secret service Vladimiro Montesinos.