Labour MPs who use the issue of intervention in Syria to try to oust Jeremy Corbyn are "playing with fire", Len McCluskey has warned.
In an exclusive blog on HuffPost UK, the Unite secretary general blasted Labour MPs for trying to use the debate to force Corbyn out.
McCluskey said that the union would resist any attempts to stage a coup against the Labour leader.
He said: “The issue of Syria is being used as the thin edge to stage a coup against Jeremy Corbyn, Labour's (overwhelmingly) elected leader.
“He has been denounced for writing to MPs and party members making his views on Syria clear - as if his huge mandate, which included support for his long-standing anti-war record, had simply earned him the right to be seen but not heard.
“Yet at the same time members of the Shadow Cabinet are making their own pro-bombing views plain, either publicly or in off-the-record briefings.
“And backbench MPs are even calling on him to quit for having the temerity to maintain his values and principles, with one even comparing him disgracefully to a 'fuhrer'. That is not open debate, it is abuse and should have no place in the party.
“The thought that some Labour MPs might be prepared to play intra-party politics over an issue such as this will sicken all decent people.
“And they are playing with fire. Any attempt to force Labour's leader out through a Westminster Palace-coup will be resisted all the way by Unite and, I believe, most party members and affiliated unions.”
On Thursday, Corbyn sent a letter to his MPs setting out why he could not support David Cameron’s case for a bombing campaign on Islamic State targets in Syria.
The letter prompted anger from members of the Shadow Cabinet and backbench Labour MPs, which in turn saw Corbyn supporters, including Labour MP Diane Abbott, suggesting they should fall in line, underlining the deep divisions in the party.
But when questioned on this Sunday’s edition of the Andrew Marr Show, the Islington North MP was defiant.
He said: “I'm not going anywhere. I'm enjoying every moment of it."
He also said that while he was not yet sure about whether he would whip his MPs on the vote, ultimately it was his decision to make.