Harriet Harman suggests that Ed Miliband would not force Nick Clegg to stand down before forming a coalition with the Lib Dems in 2015.
Those on the left of the party have been treated with contempt as Clegg seeks to transform the Lib Dems into a free market sect.
His decision to remake the Lib Dems as a centrist "party of government", rather than a centre-left outfit, could prove ruinous if the next election doesn't produce the right result.
"In the past the Liberal Democrats would eke out an existence on the margins of British politics. Now we hold the liberal centre while our opponents head left and right."
Lib Dem activists in London and elsewhere opposed Labour's introduction of the policy now adopted by Nick Clegg.
While Miliband can only complain about the "cost of living crisis", Clegg and Cameron can act now.
Lib Dem activists suggest that Clegg's position could still come under threat if the party finishes fourth or fifth in next year's European elections.
After publicly disagreeing over the danger of a new housing bubble, the Lib Dem pair find themselves at odds over the end of the coalition.
Lib Dem delegates voted by a majority of just four (224-220) not to pledge to reintroduce the 50p rate as Clegg and Farron divided.
The Lib Dem leader could face defeat this afternoon after he argues against changing "one very specific symbolic tax rate" in opposition to the party president.