The deputy prime minister will call for people to vote tactically for the Liberal Democrats to reduce the chances of a minority Conservative government propped up by rightwing parties.
British values of “decency, tolerance and generosity” would be abandoned if Ukip and Northern Ireland’s DUP propped up a Tory minority government after 7 May, Clegg will say on Thursday.
He will repeat the argument central to the Lib Dem campaign that his party would be a moderating force in a coalition with either of the two main parties, providing “heart” to a Conservative-led administration and a “brain” to a Labour-led one.
Clegg will give the speech in Cheadle, a marginal seat currently held by the Lib Dems, which is on a list of 20 seats the party says are key to keeping Blukip out.
The party is calling for people to vote tactically in its favour in the 20 seats, of which 15 are held by the Lib Dems and five by the Conservatives.
“Imagine what Britain could become if the prime minister had to bargain with [Ukip leader] Nigel Farage and his friends for votes,” Clegg will say. “Our public services cut to the bone. Our communities divided. Our shared British values of decency, tolerance and generosity cast aside.
“Instead of Liberal Democrats holding the balance of power and using it to keep the government in the liberal centre ground, Nigel Farage and his friends in the Conservatives and the DUP would drag Britain further and further to the right.”
The Lib Dems will unveil a poster showing Farage walking into No 10 alongside David Cameron, echoing Tory election posters that warn of the threat of a Labour-led government propped up by the SNP.
Later on Thursday, leaders of opposition parties will take part in a debate on the BBC, an event that Clegg says he was barred from attending.
A senior party strategist said: “Today’s debate will really be between Ed Miliband and Nicola Sturgeon … we’ve seen a lot about the threat of a possible leftwing alliance, but what we won’t see on screens tonight is the people who want to form a rightwing alliance.”
On Wednesday at the launch of the Lib Dems’ manifesto, Clegg said the question facing voters on 7 May was not so much whether Cameron or Miliband would be walking into No 10 but who would be walking in with them.
Asked whether a call for people to vote tactically was a key element of its campaign, a senior Lib Dem strategist said: “This is how the Lib Dems have won seats for decades. Get into second place and then squeeze the third party.”
A report in the Times quotes unnamed “allies” of Clegg as saying he will quit as party leader if he fails to secure a position in a coalition government.
Responding to the claim, he told BBC1’s Breakfast programme: “I don’t actually read many of these reports, and most of them of course are very, very wide of the mark. My view is very simple. As a country, we have to finish the job to make sure that we have a strong economy for the future. We’ve got to do it fairly. We’ve got to invest in things like the NHS. That means getting the balance right.”
This article was written by Frances Perraudin, for theguardian.com on Thursday 16th April 2015 10.24 Europe/Londonguardian.co.uk © Guardian News and Media Limited 2010