The Swiss authorities have called for tougher measures to combat illegal immigration.
A government report warns that illegal immigrants are increasingly involved in crime and the black economy.
The report, carried out jointly by four federal offices at the request of Justice Minister Christoph Blocher, says that up to 300,000 foreigners are residing illegally in Switzerland, with around 90,000 holding down jobs.
"The findings are no great surprise, but we now see the problems: for instance, crime among foreigners and illegal immigration from asylum seekers,” said Eduard Gnesa, head of the Federal Office for Immigration, Integration and Emigration.
“We want the foreigners who come here to stick to our rules and not become criminals,” he added.
Statistics show that in 2003 foreigners were accused of more than half the registered crimes in Switzerland – the highest level in the past ten years.
According to the 92-page report, criminal gangs based abroad are said to play a key role, especially when it comes to the drugs trade, theft and violent crime.
They are attracted to Switzerland by its high standard of living, low level of integration, short prison terms and comfortable detention conditions if convicted.
The report also highlighted the effect of illegal immigrants on the job market, where they are paid below-minimum wages and miss out on social welfare benefits.
The cantons, which are responsible for policing the labour market, have complained that there is a lack of cooperation from the home countries of illegal workers, hindering any forced repatriations.
But Jean-Michel Dolivo, a member of the “sans-papiers” collective, an organisation that supports illegal residents and workers, says the debate surrounding illegal work practices is hypocritical.
"So long as the economy needs cheap and flexible labour, it is ridiculous to try and fight illegal work," he told swissinfo.
Approximately 20,000 asylum seekers are also believed to cross the border illegally each year, says the report.
The authorities are concerned that up to 80 per cent of them throw away their identity papers, making it virtually impossible for them to be repatriated.
With around four out of five asylum requests turned down, the authorities believe most potential refugees are not fleeing their homeland because of persecution.
"What needs to be done are more controls at the borders but also inside the country,” Gnesa told swissinfo.
“Cantons should also step up their measures, but we should also make sure that asylum seekers who cooperate with the authorities get better status; those who don't toe the line should get harsher punishment.”
But Gnesa stressed that genuine asylum seekers would always find refuge in Switzerland.
The report outlines a series of measures designed to stem the influx of illegal immigrants.
While some involve little change, such as tighter border checks, other recommendations include the introduction of biometric databases for asylum seekers, new hard-to-counterfeit papers for foreigners, and tougher checks for passengers on flights bound for Switzerland.
The authorities are also considering special detention procedures for asylum seekers who refuse to leave Switzerland.
And the justice ministry is still examining whether to send foreign criminals home to serve their sentences.
“Switzerland does not want criminals coming from abroad, and people who take advantage of our system,” said Gnesa.
The report has come in for criticism from refugee support groups.
"This project only proposes repression as a solution and does nothing to encourage legal migration or to improve integration of foreigners," said Jürg Schertenleib of the Swiss Refugee Council.
But Schertenleib says the report's conclusions have the fingerprints of the Swiss justice and police minister – who is a member of the rightwing Swiss People’s Party – all over it.
"It's obvious he focused on one issue alone: illegal immigration," he told swissinfo. "There was never going to be any discussion about wider migration issues."
The report comes as parliament is discussing new asylum and foreigners’ laws, as well as legislation on illegal work practices.
Planned changes would make it more difficult for some foreigners to come to Switzerland.
swissinfo with agencies
Up to 300,000 people reside illegally in Switzerland.
Around 90,000 foreigners work without proper authorisation.
Approximately 20,000 asylum seekers are thought to enter the country illegally each year.
Around 100,000 people are turned back at the border annually.
Four federal offices are demanding in a new report harsher measures to fight against illegal immigration.
The report pinpoints work practices and crime as the biggest issues linked to illegal immigration.
The proposed measures include increased border checks, new residence papers for foreigners and possible detention for asylum seekers who refuse to leave Switzerland.
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