Sir Keir Starmer's party has set its sights on regaining Wolverhampton South West at the next general election, having lost the seat to the Tories in 2019.
But prospective candidates for the key marginal have been left in limbo after the selection process was pushed back, with Labour understood to be waiting for women applicants to come forward.
The constituency, which will become Wolverhampton West under boundary changes, has been won five times each by Labour and the Tories over the last 40 years.
The current MP is Conservative Stuart Anderson, who holds a majority of 1,661.
A Labour source told the Express & Star: "We want to make sure that local Labour members can select their candidate from a diverse range of people – with a range of skills and experience.
"More people from underrepresented communities should apply to become MPs. This selection will be opened when the Labour Party is confident that we'll get applicants from all walks of life."
Labour initially planned to have a candidate in place before Christmas.
Among the prospective candidates are Labour NEC member Mish Rahman and lawyer Warinder Juss, while Wolverhampton councillor Celia Hibbert announced she had applied for the seat last October.
Mr Rahman, from Walsall, told the Express & Star he was in the dark over the status of the selection process.
"I don't know why the selection has stopped," he said. "It is just not happening at the moment and I have no answers as to why.
"I am ready. I believe that I am the best person for it and I would rather it be over and done with.
"I can't wait to get started if selected. I'm a campaigner and I like to get my elbows dirty, but if it's not me and someone else gets selected then I'll be helping them."
All prospective candidates must pass an initial interview, before shortlisting takes place ahead of a vote of local members.
In Wolverhampton North East Sureena Brackenridge was named Labour candidate back in November, while Shadow Cabinet member Pat McFadden MP will defend the Wolverhampton South East seat he first won in 2005 for a fifth time.
The delay in Wolverhampton South West has led to frustration among some local members, one of whom told the Express & Star: "This is a seat we should really be winning yet we have not even got a candidate yet.
"Members want to be out campaigning. The party needs to get its act together."
The selection process is set to be further complicated by changes to Constituency Labour Party (CLP) membership necessitated by the upcoming boundary changes.
This means, for example, the new Wolverhampton West CLP will gain Blakenhall and Oxley ward members who are currently part of Wolverhampton South East and Wolverhampton North East respectively.
A Labour spokesperson said: "Local Labour members will have the opportunity to select their Labour candidate for Wolverhampton South West when we open the selection process ahead of a general election."
The Conservatives are also seeking a new candidate after Mr Anderson announced he was standing down.