A left-leaning Labour MP has demanded an independent review into a selection contest which she claims was “undemocratic and discriminatory” after losing to a front bench colleague.

Beth Winter has said the way in which the party chose its candidate for the Welsh seat of Merthyr Tydfil & Upper Cynon was “flawed from beginning to end”.

The sitting MP for Cynon Valley was defeated by shadow Scotland minister and Merthyr Tydfil and Rhymney MP Gerald Jones.

The two constituencies Ms Winter and Mr Jones currently represent are due to be scrapped and effectively merged into one under UK boundary changes – setting up the two-way contest between them.

In a dossier shared with the Welsh Executive Committee, Ms Winter has claimed the process made it easier to cast votes online than by post and “indirectly discriminated against older members”.

“I believe that this process is in breach of the express condition set out in the Guidance on Ballots that the selection process will be carried out ‘in accordance with the principles of the Equality Act’ and that there will be ‘no discrimination’ on the grounds of age and other protected characteristics,” she said.

She has also suggested Mr Jones had been allowed to use Labour Party resources in an internal selection campaign and failed to respond to her questions about the contest.

A lack of clarity about the start date of the process, a short voting period and an absence of in-person meetings or hustings are among other alleged issues Ms Winter has complained about.

The MP claimed that problems persisted after the count, with the procedures secretary promising to supply candidates with a breakdown of the vote which has not been provided.

She said: “My experience as outlined above presents in my view a process that is neither inclusive, fair or democratic. This leads to feelings of a lack of trust and confidence in Labour Party procedures.”

Ms Winter is among several politicians from the left of the party who have lost out on candidacies in recent months.

A row has flared up over the decision to block Jamie Driscoll, the serving North of Tyne mayor who has been described as the “last Corbynista in power”, from running in another role in the region.

Mick Whitley MP, who along with Ms Winter is a member of the left-wing Socialist Campaign Group parliamentary caucus, also lost a contest in his Birkenhead seat to shadow employment minister Alison McGovern.

John McDonnell, who was the Corbyn-era shadow chancellor, has accused the Labour leadership of allowing a “right-wing faction” to become “drunk with power” and attempt to “destroy” the left of the party.

Senior party figures have rejected the accusation, with Angela Rayner insisting that left-wing voters will not be taken for granted.

Welsh Labour has been contacted for comment.

It previously defended the Merthyr Tydfil & Upper Cynon selection process.