A council leader has said he is "absolutely horrified" over government plans to drive vans through his borough with adverts calling on illegal immigrants to leave.
Brent's Muhammed Butt said the plan was an "act of desperation" and that more needed to be done to process people's claims.
He added it would "just drive people underground".
The Home Office said the scheme was an alternative to criminal procedures.
The vans will drive through Barnet, Hounslow, Barking and Dagenham, Ealing, Brent and Redbridge.
Leaflets, posters and messages in local newspapers will also be used to urge illegal immigrants to return home.
They will all feature a text number they can message to arrange a return.
The scheme costs just under £10,000, which is cheaper than forcibly removing someone. That process costs about £15,000.
'Whose fault is it?'
Mr Butt told BBC London 94.9 he first heard about the scheme on Twitter.
"I was absolutely horrified to find that Brent had been chosen and we hadn't been consulted," said the Labour leader of the council.
"In a diverse borough like Brent when 65% of the population is from an immigrant background it's just a totally divisive policy."
He added: "It just shows what contempt national government has for local government and we have to face all the decisions made by them and they're giving us no support to move forward."
Mr Butt said Brent North MP Barry Gardiner had the highest caseload of immigration cases to look at as it was taking so long to process claims.
"So whose fault is it? Is it the immigrants who've applied and their cases are not being processed?"
The Home Office said the areas were chosen because they had either significantly higher or below average numbers of voluntary returns.
It said voluntary returns were the most cost-effective way of removing illegal immigrants and saving the taxpayer money.
Councils were not consulted as it is an immigration policy which does not require local consent, it added.
Immigration minister Mark Harper said: "This pilot is just another part of the reforms of the immigration system that have cut out abuse and seen net migration drop to its lowest levels in nearly a decade.
"The Immigration Bill being introduced later this year will build on this work by restricting illegal migrants' access to benefits and services."