But in a composed performance before a parliamentary investigation, Fischer accused his political opponents of exaggerating the scale of the problem. The opposition Christian Democrats say the revised system was exploited by criminal gangs who smuggled in women forced into prostitution, drug dealers and workers seeking illegal employment.

In his televised testimony, Fischer accepted responsibility for the directive changing the visa system.

"You can write: it was Fischer's fault," he said. "I should have been informed sooner and I have should reacted sooner. That was my mistake."

But Fischer, a leading member of the Greens party, attacked the opposition's attempts to "dramatize" the issue and defiantly dismissed claims that German security was comprised as a result of the changes to the visa policy.

"The idea that security was put in danger and that the country was flooded with criminals is simply opposition propaganda," he said. He said there was no statistical proof that crime committed by Ukrainians, who received the majority of the tourist visas, had increased in Germany as a result of the influx of immigrants.

Encouraging democracy?

Fischer was cross-examined by Christian Democrat members of the cross-party inquiry about why he failed to act earlier to close the floodgates once the scale of the problem became apparent. Current and former German ambassadors have told the investigation that they submitted alarming reports of the rush for applications as early as March 2000. The embassy in the Ukrainian capital Kiev for example issued 297,000 visas in 2001 alone, but the foreign ministry did not fully close the loophole until March 2003.

Fischer argued, however, that the original aim of the revised visa system had been to allow eastern Europeans to travel more easily into western Europe to encourage the development of democracy. And he claimed that it helped to produce last year's "orange revolution" in Ukraine when the pro-western Viktor Yushchenko won the re-run presidential election after a popular but peaceful uprising.

"The orange revolution would never have been possible if Ukraine had not opened up," Fischer said.

Reports say that many of the Ukrainians who entered Germany went on to work illegally on building sites there and in other European Union countries.

Resignation ruled out

The visa scandal has cost Fischer, a former student rebel turned international statesman, his long-standing position as Germany's most popular politician. Yet Fischer has the support of Chancellor Gerhard Schröder and has ruled out resigning over the visa issue.

His day-long testimony comes less than a month before a key election on May 22 in Germany's most heavily populated state, North Rhine-Westphalia. With the Greens bound together with Schröder's Social Democratic Party (SPD) in the ruling coalition, Fischer's performance in front of the inquiry could have an impact on the state election.

A general election is due in September 2006 and the SPD would be seriously weakened if it were to lose the state poll in North Rhine-Westphalia, one of its traditional strongholds. SPD chairman Franz Müntefering (photo)called on Fischer to give a clear account to the investigation in order to repair the political damage done by the visa scandal.

"The affair has unsettled our voters more than the Green voters," Müntefering said at the weekend.

One tactic used by the criminal gangs was to book thousands of eastern Europeans into German hotels in order to have the address required for a visa, but most never arrived at their stated destination, according to a report in Monday's Tagesspiegel newspaper.