A senior church leader has called for an end to "alarmist" rhetoric on immigration as Nigel Farage prepared to launch Ukip's campaign for the European elections amid controversy over the party's new poster campaign, which has been called "racist" by critics.
Cardinal Vincent Nichols says the stark messages about direct threats to UK workers' jobs from millions of unemployed Europeans are "a hard-hitting reflection of reality".
The anti European Union (EU) party is using £1.5 million of funding from millionaire ex-Tory donor Paul Sykes to launch its biggest-ever publicity drive ahead of the May 22 poll which many observers believe it could win.
Cardinal Nichols, the leader of the Catholic Church in England and Wales, said it was wrong to use expressions that suggest "dismay or distress at all these people coming to this country".
He did not refer to any particular party in the comments he made to The Daily Telegraph, but appealed to all sides to celebrate the contribution of immigrants rather than "anger and dismay".
"What I would appeal today is that the debate about immigration is done with a sense of realism and a sense of respect - and that it is not cushioned in expressions which are alarmist and evocative of anger or of dismay or distress at all these people coming to this country," he said.
The Ukip posters are to be displayed at hundreds of billboard sites across the country, carry stark warnings that "British workers are hit hard by unlimited foreign labour".
Another says that 26 million people in Europe are looking for work, adding by a picture of a finger pointing at the reader "and whose job are they after?".
Under the slogan "take back control of our country", others complain that 75% of British laws are made in Brussels and that UK taxpayers fund the "celebrity lifestyle" of EU bureaucrats.
Mr Farage, who will formally launch the campaign in Sheffield on Tuesday, dismissed the concerns of the "chattering classes".
"These posters are a hard-hitting reflection of reality as it is experienced by millions of British people struggling to earn a living outside the Westminster bubble," he said.
"Are we going to ruffle a few feathers among the chattering classes? Yes. Are we bothered about that? Not in the slightest.
"Ukip is hugely grateful to Paul Sykes for his magnificent contribution to the great cause of restoring Britain's ability to be a self-governing nation. The political earthquake I have spoken of is on its way."
Mr Sykes said: "An overwhelming victory for Ukip will break the political mould in the UK, forcing Labour and the Lib
Dems to back a full-scale referendum and intensifying the popular pressure for that to be staged as early as general election day 2015."
Nick Clegg appealed for help from Labour and pro-EU Tories to counter Ukip's arguments in the run-up to May 22 and dismissed Mr Farage's claims to be an insurgent.
He wrote in The Guardian that Ukip is part of the anti-Brussels "establishment" and its leader is the sort of professional politician he accused others of being.
"Of all Nigel Farage's far-fetched claims - and there are many - the most outlandish is the idea that Ukip's call for an exit is the insurgents' battle cry," he wrote.
"What poppycock. For a start, Farage is every bit the professional politician he enthusiastically reviles. He and I were elected to the European Parliament on the same day in 1999. I left after five years. The Ukip leader is still there.
"More important, there is nothing remotely new about his party's ambitions. Ukip is simply the fresh face of a long-standing Eurosceptic establishment, supported by many in the Tory party and significant parts of the press."
Mr Clegg acknowledged that a British exit from the EU was now "plausible" but insisted he would happily take on Mr Farage in more televised debates - despite being widely seen as having lost support to him after the two already broadcast.
Admitting the pro-EU case lacked "volume", he said: "The Lib Dems have started this debate - but we cannot win it alone.
"We want to work with others to deliver the firepower needed to challenge the Eurosceptic establishment.
"If Labour is still a pro-European party, it needs to come off the fence. Tory modernisers must risk the wrath of their backbenchers and speak out."