Michael Dugher became the first casualty of Labour leader Jeremy Corbyn's shadow cabinet reshuffle as he was sacked from the post of shadow culture secretary.
In a message on Twitter, the Barnsley East MP announced: "Just been sacked by Jeremy Corbyn. I wished him a happy new year."
Mr Dugher, a close ally of former prime minister Gordon Brown, voted in favour of UK military action in Syria in last month's free vote in the House of Commons. He had warned Mr Corbyn he would end up with a "politburo of seven" at the top of the party if he attempted to use a reshuffle to surround himself with allies from the Labour left.
Mr Corbyn is expected to use the first day of the Commons' return from Christmas recess to finalise the shake-up of his top team, after late-night talks with key members of the shadow cabinet ended without any announcement on Monday.
A spokesman for Mr Corbyn said the leader had "several discussions in relation to changes to the shadow cabinet" but would not give any details of who, if anyone, was being moved or sacked.
The talks followed speculation of a possible "purge" of those with views at odds with the leader, such as shadow foreign secrretary Hilary Benn's Commons speech in favour of RAF air strikes in Syria and shadow defence secretary Maria Eagle's support for the renewal of the UK's Trident nuclear deterrent.
Another nine shadow cabinet members voted for air strikes after Mr Corbyn was forced to allow a free vote - fuelling suggestions that he could replace them with left-wing supporters.
But the scope of the changes appeared increasingly likely to end up narrower than mooted, as the leadership sought to balance the desire for a coherent message on the front bench with the major backlash in the parliamentary party that would greet any move to freeze out moderates.