By Isla Binnie

ROME, June 13 (Reuters) - Rome mayor Virginia Raggi, a prominent member of the anti-establishment 5-Star Movement, has asked the government not to send any more asylum seekers to the capital, saying it is already groaning under the strain.

The request was made public on Tuesday, after 5-Star took a drubbing at local elections on Sunday, failing to make the run-off in 24 of the main 25 cities called to pick a mayor. A national vote is due by the first half of next year.

Managing newly arrived migrants has become one of the thorniest issues for Italy's government, which is run by the Democratic Party (PD), the 5-Star's rival.

More than half a million people have arrived by boat from North Africa since 2014, and almost 200,000 are being housed in state-funded centres while they put forward asylum requests.

Raggi wrote to the interior ministry, which is responsible for plans to relocate asylum seekers from arrival points on the southern coasts to the rest of the country, asking to suspend further arrivals to the capital, her spokesman said.

"This administration hopes the decisions about where to put new centres will take into account the evident pressure migration is putting on Rome, and the consequences which may be devastating socially and for the protection of the people they are built for," Raggi said in the letter.

5-Star has made ambivalent statements about immigration in the past, and its potential prime minister candidate Luigi Di Maio has accused humanitarian groups of running a "taxi" service for boat migrants from Libya.

Pollster Renato Mannheimer said the anti-immigrant tone was probably a bid to appeal to rising fears among Italians that foreigners would crowd them out of an already tight job market, and could undermine security.

"A growing number of Italians, roughly half, say we should not be taking in more migrants," Mannheimer said. 5-Star "needs to get back support in the usual way, and this topic is ideal."

Only around a third of Italy's 8,000 city governments have offered to shelter asylum seekers. In Rome, police have repeatedly cleared out temporary camps for people trying to reach Northern Europe, citing security concerns.

Andrea Costa, director of the Baobab Experience volunteer group which has set up impromptu kitchens and tents for migrants in a run-down area of eastern Rome, derided Raggi's letter.

"With a wink at the worst of the xenophobic right wing, Raggi hopes to bounce back from her movement's electoral flop," Costa wrote on Facebook. (Additional reporting by Gavin Jones; Editing by Richard Balmforth)