The United Nations refugee agency has written to Rome's mayor Virginia Raggi in protest at the hundreds of migrants sleeping rough on the streets of the capital, where thousands more with legal residence are living in squats.
The UNHCR said Rome's authorities could ignore thousands of refugees and other people granted permission to remain in Italy who lacked adequate shelter in the city.
"This reality means there has to be reflection on developing concrete integration policies," UNHCR said in its letter.
"We have been highlighting this problem for months and our worries have only increased," said Carlotta Sami, UNHCR's spokeswoman in Italy.
Sami said Rome could learn from the northern city of Milan whose authorities have established a migrant reception "hub" to stop migrants being forced to sleep out of doors as the cold winter weather sets in.
There has been a surge in the number of migrants sleeping on Rome's streets since the city council closed a large informal reception centre near the Tiburtina rail station last year. The often makeshift camps that have sprung up are regularly dismantled by the authorities, making it more difficult to track and assist migrants.
Raggi, a member of the populist Five Star Movement, who was elected mayor in a landslide victory in June, said recently that her administration's priority was to stop the influx of migrants into the city.
"If we set up 100 tents, in two days we will have to provide 100 others," she argued.
The highest-ever number of boat migrants have reached Italy this year - 171,299 - a figure that already topped the record 170,100 who arrived in the whole of 2014, the Italian interior ministry said on Monday.
As other European states tighten their borders, more migrants than ever are having to stay in Italy while their asylum-applications are processed, straining the country's reception facilities to the limit.
Italy has capacity to house up to 200,000 migrants and in the past three years has recorded nearly half a million migrant arrivals.
