Jeremy Corbyn is facing a backlash from Labour MPs after it emerged that the man he appointed as his political adviser described Ed Milband’s shadow cabinet as “the most abject collection of absolute shite”.

Andrew Fisher, a former union activist, also referred to Tony Blair and Alastair Campbell as “scumbags”, called Jack Straw a “vile git” and accused Yvette Cooper of pushing “racist” policies when she was shadow Home Secretary. Mr Fisher, a prominent figure on the left who was one of Mr Corbyn’s first appointments, is also facing accusations of party disloyalty for backing an anarchist candidate against Labour at the election and taking to Twitter to celebrate the downfall of the shadow Chancellor, Ed Balls.

Andrew Fisher's Twitter profile picture

On the morning after the election, as Labour reeled from the news that Mr Balls had lost his Morley and Outwood seat, a message on Mr Fisher’s Twitter feed read: “Fitting that the architect of Labour’s miserable austerity-lite economic policies should lose.”

The decision to employ Mr Fisher in the Labour leader’s office set off an angry exchange during the weekly meeting of the Parliamentary Labour Party on 19, The Independent can reveal.

Andrew Fisher on... Show all 4 1 /4 Andrew Fisher on... Andrew Fisher on... Tony Blair and Alastair Campbell A tweet from July 2014 by Fisher described the pair as ‘scumbags for hire to scumbags’ AP Andrew Fisher on... Ed Balls and Yvette Cooper Fisher celebrated Balls’s election defeat the morning after. A few weeks later, he described Cooper’s welfare policy as ‘vile and racist’ Getty Images Andrew Fisher on... Rachel Reeves Last November, Fisher tweeted that the then shadow Work and Pensions Secretary ‘seems to have defected to Ukip this morning’ Getty Images Andrew Fisher on... Jack Straw In February of this year, Fisher described Jack Straw, former Home Secretary, as “a vile git.” Getty Images

Two MPs, Caroline Flint and Siobhan McDonagh, demanded to know why Mr Corbyn was employing someone accused of openly attacking Labour during Mr Miliband’s time as leader. A spokesman for Mr Corbyn said: “We are aware of this. We’re not commenting on it.”

One tweet, posted on Mr Fisher’s Twitter feed on 2 July 2014, described Mr Blair and his former communications chief, Alastair Campbell, as “scumbags for hire to scumbags”. Another, dated 12 September 2014, declared that “the Labour front bench is the most abject collection of absolute shite”.

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In a tweet in May, a few weeks after the election, he described a policy advocated by Yvette Cooper on welfare payments as “vile and racist”, shortly after comparing it with the policy of the far-right British National Party.

Labour MP Caroline Flint has demanded an explanation (Getty Images)

Another, last November, was aimed at the then shadow Work and Pensions Secretary, Rachel Reeves. It read: “Oi, Ed Miliband! Have you noticed Rachel Reeves seems to have defected to Ukip this morning?” On 22 February this year, he described Jack Straw, former Home Secretary, as “a vile git.”

Mr Fisher’s Twitter feed also gave vent to his republican sympathies. The occupants of Buckingham Palace were described in one tweet in January this year as “bastards” and Prince Andrew was denounced as a “parasite”.

It is understood that Mr Fisher is already the subject of an internal investigation because of a tweet that urged voters in Croydon South not to vote for the Labour candidate, Emily Benn. Instead he supported Jon Bigger, a candidate for the anarchist group, Class War.