Medical charity Doctors Without Borders said the Italian government had refused to renew its permit to help immigrants arriving on the southern island of Lampedusa, forcing it to cease operations there.
The France-based group, also known as MSF, had been providing free emergency medical screening since 2002 at the small harbour of Lampedusa, an immigration hotspot in Italy where thousands of people, especially from Africa, arrive every year.
Loris De Filippi, the head of MSF operations in Italy, said the aid agency had left the island on October 31 after the Interior Ministry refused to give it the necessary authorisation to keep working there.
Speaking to Reuters by phone, De Filippi said the government had told MSF that local health facilities could handle the flow of immigrants, many of whom come to the island on rickety boats, often after days without food or clean water. "The number of arrivals has risen, the seriousness of people's conditions is getting worse and even the type of people is changing -- now we are getting more children and women, some of them pregnant," De Filippi said.
Thirty percent of arrivals in recent months came from war zones or countries affected by drought in the Horn of Africa, he said.
"We would be happy to leave it all in the hands of the national health system, but we feel they are not able to cope, nor are they willing to," he said.
Lampedusa has limited hospital facilities.
Left-wing lawmakers from the Radical party on Thursday demanded the conservative government led by Silvio Berlusconi explain its position in parliament.
Last week the head of the Interior Ministry's immigration department, Mario Morcone, said Lampedusa had adequate health facilities and MSF's help would be more useful in other areas of Italy.
Morcone said the group could stay on the island if it wanted, but hinted at strained relations, saying that it should be "more humble" in its dealings with local officials.
MSF has in the past criticised both centre-right and centre-left governments in Italy, denouncing what it considered a lack of adequate immigration policies and the squalid conditions of holding centres for illegal immigrants.
"It is unacceptable that while MSF medical teams can operate at the heart of the North Kivu conflict in the Democratic Republic of Congo, we are practically forced to stop humanitarian and medical assistance on the territory of a European nation," De Filippi said.
He said MSF had tended to 4,550 migrants in Lampedusa since 2005, including 1,420 between January and October 2008. Overall, some 25,000 people have arrived in Lampedusa this year.
The deputy mayor of Lampedusa, Angela Maraventano of the anti-immigration Northern League, told the ANSA news agency MSF operations would be more useful in other countries.
"In Italy we have the public health service, by improving it we can help everybody: immigrants, and above all residents."