Two Labour whips - south Armagh-born Conor McGinn and Holly Lynch - have resigned following the sacking of chief whip Rosie Winterton in Jeremy Corbyn's controversial frontbench shake-up.
The removal of Ms Winterton provoked an angry backlash, with chairman of the parliamentary party John Cryer writing to MPs to protest that he and the chief whip had been kept in the dark about the reshuffle despite being engaged in talks with the leadership on putting some of the posts in the shadow cabinet up for election.
A Labour spokesman said: "We thank Conor McGinn and Holly Lynch for their services. Their positions will be filled in due course."
A Labour source said: "No-one will lose any sleep over Conor McGinn resigning after the disloyalty he showed in organising resignations during the attempted coup."
Sources close to Mr Corbyn insist that Mr McGinn was set to be sacked when junior posts in the reshuffle were announced.
Bessbrook-born Conor McGinn is the son of former Newry Sinn Fein councillor Pat McGinn.
In July, Mr McGinn claimed he had come under pressure after he urged the party leader to broaden his appeal in an interview in May. He claimed Mr Corbyn, who has supported Irish republican causes, had proposed to ring his dad to discuss the comments.
"It transpired that Jeremy, in deliberations about how to respond to my interview, had said that he intended to ring my father to discuss it with him and ask him to speak to me about it," the MP said at the time.
Mr McGinn, a former political adviser to the last shadow Northern Ireland secretary, Vernon Coaker, also said he had been subjected to bullying and threats from Corbyn supporters and had to have a police presence at events he was attending last weekend.