The Lib Dems will be annihilated at the election if they try to be a "permanent see-saw coalition partner", the party president Tim Farron will warn tomorrow.
In a speech to the Social Liberal Forum conference in East London on Saturday, Farron, who is on the left of the party an seen as a likely leadership contender when Nick Clegg steps down, will also warn that the Lib Dems will not survive it they try to position themselves to the liberal right on the economy.
"There is no political market for a centre right laissez faire liberal party amongst the British electorate, or for a party that sets itself up as the permanent see-saw coalition partner," he will say.
"To aim to be either would be to neuter our movement and invite electoral annihilation on the same scale of our friends in the German FDP who chose a similar path. To follow the FDP example would be to abdicate responsibility for our economy."
In 2009 the FDP won enough votes in the federal German elections to become the junior partner in a coalition government with Angela Merkel's CDU. However in the 2013 election its support slumped below the 5% national vote threshold needed to secure any seats in the Bundestag. Its failure to also win any directly elected seats means the party has no representation in the German parliament for the first time since 1949.
Farron's intervention will be seen by some in the party as a coded criticism of Clegg. The deputy prime minister has indicated he would be equally prepared to do a deal with either Labour or the Tories after the election in the event of another hung parliament, but that it would have to be a formal coalition government or nothing.
A key part of the Lib Dem leadership's sales-pitch to voters is the success the party has had in blocking right-wing Tory policies including an inheritance tax cuts for millionaires.
However Farron will say the party needs to set out a positive message. "Politics should be about positive plans for a better Britain, not fear and loathing for one tribe or another. We should want the British people to choose the Liberal Democrats for what we are for, more than who we are against," he will say.
This week a YouGov poll showed the Lib Dems support had slumped to just 6% and with the general election less than ten months away, the party is running out time to turn those numbers around.
In his speech, Farron will call for his party to "stake out the case for comprehensive liberalism based on a true understanding of what creates and what prevents freedom".
"Laws that prevent you worshipping as you choose, living with whom you choose, reading what you choose curtail your liberties no more and no less than the poverty, the ill health and the inadequate education that robs you of your choices," he will say.
"Never mind economic liberalism versus social liberalism," he will add. "I demand that Liberals should defend our citizens from all of those threats... our new consensus must be based on a belief in active, can do government whose focus is on tackling the biggest challenges we face in the confident belief that we can overcome them."
Farron will also call for the government to set a target for "every breadwinner to be paid a living wage by 2020" to stop the "scourge of in work poverty"
And he will tell delegates about his personal life story of growing up in a terraced house in Lancashire with "no heating, no holidays" and attack the "appalling rhetoric of Miliband and Osborne – setting the shirkers against the striver".