Labour is re-opening the selection for their candidate to replace Joe Anderson as Mayor of Liverpool.
The party had initially shortlisted three female candidates to take over the post from Anderson, who has stepped aside because of a police investigation.
But, despite campaigning getting well underway, they have now been told they should not continue - or reapply.
The move has been called a "undemocratic failure of process" by one candidate who took to Twitter to express her anger at the decision.
Acting Mayor of Liverpool Wendy Simon, Ann O'Byrne the former Deputy Mayor of Liverpool, and current Lord Mayor Anna Rothery had been selected to run for the position.
But as ballots were set to be delivered and voting begin, the process was suddenly suspended, and all three candidates re-interviewed.
Anna Rothery called the decision "chaotic" and said she would have no choice but to launch a legal challenge if the decision was not corrected.
In a statement on her Twitter page the current Lord Mayor says she is "shocked at the party's chaotic handling of the selection for Liverpool mayor", adding, "instead of a positive unifying campaign for our city we are faced with what looks like an undemocratic failure of process."
A Labour spokesperson said, "After careful consideration, Labour is re-opening the selection for Liverpool Mayor.
"We are committed to ensuring members are able to choose the right candidate to stand up against the Conservatives, lead Liverpool out of the coronavirus crisis and fight for the resources that the city desperately needs."
The Labour party's decision comes after Joe Anderson was arrested on 4 December on suspicion of conspiracy to commit bribery and witness intimidation as part of an investigation into building and development contracts in Liverpool.
The directly elected mayor of the city says he is innocent of any allegations.
Despite being already selected as Labour's candidate to run for a third term as mayor, Anderson has been administratively suspended by the party pending the ongoing investigation.
He was re-bailed for a second time at the beginning of February.
In January Anderson said while still on bail and under investigation it would restrict and restrain him from functioning as the mayor after initially announcing he was to temporarily "step back" after his arrest.
His statement continued: "I maintain that the police investigation will confirm I have done nothing wrong, and my name and reputation will be exonerated.
"However, it is now clear that the speed of the police investigation means it will not conclude in the next few days as I hoped.
"The timing of the extended bail notice means that it is in the best interests of the Labour Party to select a new candidate for the mayoral election.
"I will continue to fight to both demonstrate that I am innocent of any wrongdoing, but also to protect my legacy as mayor of my city of which I am proud."
Anderson, who became mayor in 2012, cited his faith and thanked his family for support.