US Edition The Advertising Standards Authority is to examine whether the billboards targeted at illegal immigrants were offensive and whether a statistic quoted in them was misleading.
The billboards were carried on vans in several areas in London as part of a pilot. Ministers are considering rolling them out nationally.
However they have provoked strong opposition from the Liberal Democrats. Nick Clegg, the Deputy Prime Minister, described the vans as "aimless" and "unsettling" while Vince Cable, the Business Secretary, said they were "stupid and offensive".
Nigel Farage, the Ukip leader, described the vans as "un-British" while Eric Pickles, the local government secretary, yesterday became the first Tory minister to question their use.
However, Downing Street has claimed there is evidence that the "go home" immigration campaign is "already working" and suggested the scheme could be rolled out across the country.
The Advertising Standards Authority will investigate whether the vans breached rules because they were "offensive". It is also examining whether a statistic used on the vans, which claimed there were "106 arrests last week in your area", was misleading.
A spokeman for the ASA said: “Complainants have expressed concerns that the ad, in particular the phrase “Go Home”, is offensive and irresponsible because it is reminiscent of slogans used by racist groups to attack immigrants in the past and could incite or exacerbate racial hatred and tensions in multicultural communities.
"Separately, some complainants have challenged whether the claim ‘106 arrests last week in your area’ is misleading. They’ve also challenged whether it is misleading because it implies arrest is the automatic consequence of remaining in the UK without permission.”