Theresa May under pressure to scale back crackdown on suspected illegal immigrants amid mounting criticism of 'racist' spot checks

Tories fear spot checks and billboards are a political gift to Ukip

A controversial advertising campaign urging illegal immigrants to go home is causing rows among the coalition (PA)

Theresa May, the Home Secretary, was under growing pressure from within Tory ranks last night to scale back the tough new crackdown on suspected illegal immigrants amid mounting criticism of her department’s tactics.

The Independent disclosed last week that officials had conducted a series of “racist and intimidatory” spot checks at railway stations in areas with large ethnic minority populations.

It followed controversy over a campaign in which trucks carrying the message “go home or face arrest” toured several London boroughs.

Both schemes were signed off by the Home Office. But the Liberal Democrats have condemned them, insisting they were not Coalition policy.

It emerged that Lynton Crosby, the Conservatives’ chief election strategist, who had been widely assumed to be behind the trucks scheme, feared the initiative had played into the hands of the UK Independence Party (Ukip).

He is understood to have made his displeasure clear during a private meeting with a lobbying company in London, agreeing that the initiative had created an unnecessary row over tactics and distracted from policy.

It also gave a platform to Ukip’s leader, Nigel Farage, who condemned the initiative as ill-conceived and “unBritish”, Mr Crosby agreed.

Downing Street has suggested the billboard scheme could go nationwide and insisted it was already working, although it could point to no firm evidence that was the case.

Meanwhile, the spot-checks have triggered an investigation by the Equality and Human Rights Commission for possible unlawful discrimination.

A black Tory adviser, Derek Laud, said yesterday he feared his party’s next general election campaign would resort to dog-whistle tactics on race.

Writing in The Independent on Sunday, Mr Laud protested that it was no coincidence that immigration was being raised as an issue by his party and bemoaned that more liberal attitudes to race were being sidelined.

“I have never called anyone racist. It is an often used and discredited cry. But this time, I believe the Conservative Party has shown it is racist. It will do anything, right or wrong, to bolster its poll ratings. Cameron's hard work around a modernity agenda ran into the sand. His party has never really embraced change, but he gave up the fight too soon,” he wrote.

The station spot-checks also came under fire from Martin Ruhs, a member of the Government's migration advisory committee, who warned against the draconian approach taken by other nations.

“In liberal democracies generally we don’t want to do the kinds of things that are commonplace in Singapore or maybe the Middle East,” he told the Observer.

“You have to draw the line somewhere. Different people will draw the line in different places over what is acceptable in how you treat people.

“Obviously the government has to do something about irregular immigration, but the issue is more complex than many policymakers believe. Some policies have an element of a spectacle – you want to send a signal, and those policies aren’t necessarily the most effective.”