Downing Street holds that the Home Office’s threatening advertising campaign urging irregular migrants to voluntarily return home is working.
The PM's official spokesman said David Cameron disagreed with Lib Dem Business Secretary Vince Cable's view that the scheme was "stupid and offensive", BBC reported.
The Home Office is "clear that this is already working", the spokesman said.
Without giving figures on levels of response, the spokesman said the Home Office was "looking at what they can take forward" from the London pilot scheme.
The campaign was strongly criticised by Mr Cable who told the BBC's Andrew Marr Show on Sunday: "It was stupid and offensive. I think it is very unlikely it will continue."
Mr Cable questioned whether illegal immigrants would have enough of a "sophisticated grasp of English" to be able to read the posters on the vans at a distance.