Corbyn was the shock winner of the party’s September 2015 leadership contest despite only being initially nominated in the name of party debate.

In a twist worthy of a political farce, however, Corbyn, a former habitual rebel, won by a landslide, trouncing established contenders Andy Burnham and Yvette Cooper.

Since his election, the party has been split between centrists who broadly identify with the policies of former Labour prime ministers Tony Blair and Gordon Brown and left-wingers, particularly grassroots activists, who voted in Corbyn as leader.

The divisions were laid bare last month when, given the freedom to vote with their consciences, 66 of 232 Labour MPs, led by foreign affairs spokesman Hilary Benn, voted against Corbyn’s anti-war line, and in favour of extending British airstrikes on Islamic State jihadist targets from Iraq into Syria.

All the focus was on whether Corbyn would sack Benn, with rumours swirling that if he was axed, other centrists would quit the shadow cabinet en masse.

But the drawn-out reshuffle was limited to sacking Europe spokesman Pat McFadden and culture spokesman Michael Dugher, for what a source in Corbyn's inner circle called “acts of disloyalty”, and demoting defence spokeswoman Maria Eagle.

In the wake of the Paris attacks, McFadden had asked Cameron if he agreed the cause of terrorism was not always Western policy, and terrorists were themselves responsible for their actions. Corbyn took that as an attack on his views.

Eagle, who favours retaining Britain’s nuclear deterrent - a common view with Labour MPs but not with the party members or Corbyn - was shunted to Dugher’s old culture brief, and replaced by Corbyn’s fellow unilateral nuclear disarmament supporter Emily Thornberry.

Following the reshuffle, three other frontbenchers quit in protest.

Jonathan Reynolds and Stephen Doughty left over McFadden's sacking, Doughty quitting his junior foreign affairs brief live on BBC television, saying Corbyn's office had told “lies” about why McFadden had been dismissed.

Kevan Jones then quit as a junior defence spokesman over the way Eagle was edged aside.

“Jeremy was elected with the strapline ‘straight-talking, honest politics’,” Jones told BBC radio.

“There has been nothing straightforward or honest about what's gone on over the last 48 hours.”

Moderates fear moves to purge them gradually from the party on Corbyn’s watch.

Labour MP Ian Austin summed up the reshuffle as Dugher being sacked “for calling for unity”, McFadden “for criticising IS” and Eagle “moved for backing party policy”.

Labour finance spokesman John McDonnell, a close Corbyn colleague, said the trio were from a “narrow, right-wing clique” who disrespected Corbyn’s mandate.

Cameron has been making merry at Labour’s expense.

The Conservative leader said other European prime ministers were often asking him “'What on Earth has happened to the British Labour Party?'”.

Given the reshuffle, Cameron said Corbyn “couldn't run anything”, let alone the government.

Corbyn’s position could ultimately be decided by Labour’s performance in upcoming local and regional elections in May.

The latest opinion poll, conducted in mid-December by YouGov, put the Conservatives on 39 per cent and Labour on 29 per cent.

Nick Turnbull, a politics lecturer at the University of Manchester, said the situation inside Labour was “nuts”.

The reshuffle exposes “major divisions inside the parliamentary Labour party”, he said.

“It really seems impossible to go on like this”, he said, but “those divisions will go on and on” because Corbyn “doesn't have enough people from the hard left with him” in parliament.

“How can you run a party when everyone expects half of the party to resign?”