Chuka Umunna has used his first major speech as a Liberal Democrat MP to launch a furious attack on Labour and Jeremy Corbyn .
Mr Umunna, who once stood to lead Labour before a string of defections saw him join the Lib Dems, slammed Mr Corbyn as an "apologist for a hard-right Russian government who thinks it can poison people on British soil".
He said that that it had become "acceptable to abuse"opponents of the left-wing leader under the current regime.
The Lib Dem foreign affairs spokesman also attacked Boris Johnson as a "peddler of hate" but saved his strongest criticism for Mr Corbyn.
Mr Umunna left the Labour party in February this year alongside other disaffected MPs to form the ill-fated Change UK.
After a poor result in the European elections, he abandoned the party and sat briefly as an independent, before joining the Lib Dems.
He used his first conference speech as a member of the party's frontbench to attack his former party's handling of anti-Semitism.
Speaking directly to his former Labour, Mr Umunna said: "You cannot be a champion of liberalism if you are currently subject to a formal investigation by the Equality & Human Right Commission for institutional racism against Jewish people.
"You cannot be a champion of liberalism when your leader's supporters think it is acceptable to abuse, vilify and deselect anyone who dares to question the leader.
"And you cannot claim to be liberal when the political editor of the BBC needs to take a bodyguard to your conference."
Comparing Jeremy Corbyn and Boris Johnson he said that "neither is fit to lead the country".
He praised previous Labour grandees Clement Attlee and Ernest Bevin for their roles in founding NATO but said the party had lost its way.
He accused Mr Corbyn of "lauding authoritarian regimes in Venezuela and Iran".
"Attlee and Bevin helped found NATO - Jeremy Corbyn and those around him want to abolish it."
Last week Mr Umunna said he would not stand for reelection in the Labour stronghold of Streatham he has represented since 2010.
Instead he is will stand in the seat of Cities of London and Westminster against Tory Mark Field.
