A left-leaning MP has asked for an independent review of a selection process which she lost to a shadow minister.
Beth Winter, who has been Cynon Valley's MP since 2019, missed out on selection as the Labour Party's candidate in the newly formed constituency of Merthyr Tydfil and Upper Cynon.
Gerald Jones, shadow Scotland minister and MP for Merthyr Tydfil and Rhymney, was selected as the candidate.
After the result, Mr Jones thanked Ms Winter for a "comradely campaign" and Welsh Labour defended the process.
Momentum, the grassroots Labour-supporting organisation on the left of the party, has previously claimed the result was part of a bid to "purge socialists and install [Keir Starmer] loyalists".
In a statement on Wednesday, Ms Winter said Labour's candidate selection process was "unfair, undemocratic and discriminatory".
"Information and explanation were withheld from me at every stage of the process, which was pushed through in an unusually short timeframe for reasons that remain unclear," she said.
"Voters were disenfranchised by extremely tight deadlines, an inexplicable freeze date, a complete lack of clarity and in some cases because they did not have email addresses."
Sky News understands the process agreed by the WEC was over the course of three weeks and that members were given an opportunity to cast a proxy or postal vote.
Ms Winter confirmed she had written to the Welsh Executive Committee (WEC) to request an independent review of the selection process in Merthyr Tydfil and Upper Cynon.
The number of constituencies in Wales will be reduced from 40 to 32 at the next General Election as part of the boundary review.
In the Senedd, there are plans to increase the number of members from 60 to 96.
A Welsh Labour spokesperson said it was "regrettable" the boundary review meant the MPs had "been forced to stand against one another".
"The selection procedure was designed to give all members across the new seat a chance to take part in selecting their candidate and as a result we saw a very high turnout," the spokesperson added.
Former shadow chancellor John McDonnell previously said Keir Starmer supporters in a "right-wing faction" of the party were "drunk with power" and orchestrating a purge of the Labour left.
A number of left-leaning members say they have been prevented from running as candidates, while others say they have been wrongly expelled from the party.