Welsh Labour MP Jo Stevens is backing Owen Smith in the Labour leadership contest.
The Cardiff Central MP had been considered as one of Jeremy Corbyn's most loyal supporters - she was one of 40 MPs who refused to back the no confidence motion in their leader.
But she has now told supporters she will back the Pontypridd MP in the leadership contest.
In an email to party members, Ms Stevens wrote: "During the past two weeks it has become painfully obvious that we have been unable to fulfil the very basic day to day operation as the official opposition in Parliament.
"We cannot present ourselves as a government in waiting without leadership and a leadership team that commands the respect and support of not only members....but Labour voters and potential Labour voters."
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