There is evidence of the "widespread use of racist, aggressive and militarised rhetoric" against foreigners on social networks, said a press release issued by 12 independent groups including Maruah, Singapore's main human rights group.

It warned of a worrying trend "blaming foreigners for social ills" such as overcrowding, local unemployment, often posted anonymously online.

"We, the undersigned, are alarmed by the recent surge of racism and xenophobia in Singapore," the statement said.

It added the key to addressing frustrations felt by many Singaporeans was for the government to change the policies which caused marginalisation and inequality.

"These inequitable policies were not instituted by migrants and will not automatically disappear if the migrant population decreases," the press release said.

Among the other signatories were organisations advocating women's and migrant workers' welfare, gay rights.

The statement came a day after a Philippine independence day celebration scheduled for June 8 in downtown Singapore was cancelled following a virulent campaign by online commentators.

Migrant workers from South Asia have also been attacked and ridiculed online following a riot last December triggered by the death of an Indian worker in a road accident.

Western expatriates seen to have behaved arrogantly have also been denounced by Singaporeans.

- increased prejudice -

One wealthy British man was forced to leave the country along with his Singaporean wife and their son, after a backlash over comments he made mocking poorer citizens.

A survey by Singapore's government-linked Institute of Policy Studies released this year showed that over 30 percent of citizens and permanent residents felt that nationality-based prejudice had risen over the past five years.

This is despite a per capita income of $55,183, one of the highest in the world, and an unemployment rate of just over two percent.

Singapore's low birth rate prompted the government to grant an average of 18,500 new citizenships every year between 2008 to 2012 -- helping the population surge by 30 percent since 2004 to 5.4 million last year.

Out of a foreign population of 1.55 million, about 700,000 are mainly Asian work-permit holders employed in construction and other sectors shunned by Singaporeans. Some 200,000 others work as domestic helpers.

Singapore's long-ruling People's Action Party has tightened migrant inflows since suffering its worst showing in a 2011 general election where the large foreign presence was a big issue.

In the statement, the Singapore activists said the government was partly to blame for the marginalisation of guest workers, "for instance by not giving domestic workers full and equal employment protections".

They warned that discrimination not only oppressed the migrant community, but also reinforced discrimination against Singapore's own minorities.

Singapore's citizen and permanent resident population of 3.84 million is 74 percent ethnic Chinese, 13 percent Malay and nine percent Indian, with the rest made up of other immigrant groups.