Security firm G4S has rejected pleas from the Labour party to provide security for its conference next month, increasing the chances of the event being cancelled altogether.
Labour has been seeking a provider for its annual conference - this year in Liverpool - with the Home Office warning that it could block the event if it cannot find adequate security for the four day event.
G4S had provided security at party conference for roughly 20 years, but Labour's NEC passed an embargo on working with the firm late last year, citing concerns on its work in international detention facilities.
However, union GMB is engaged in a dispute over recognition with the only alternative provider, Showsec, and is threatening to picket the conference if the firm is chosen.
So this week, the party went back to G4S, flouting its own embargo, only to be rejected by the security firm.
G4S UK managing director for events Eric Alexander, said the firm would be unable to work on such a large event at short notice.
"Security officers need to be cleared and accredited to work, detailed risk assessments made, safety and security plans with the Home Office and local police forces drawn up and supporting logistics, such as security equipment and staff accommodation, put in place," he said.
"Safety for delegates and our staff is our priority and at this late stage and with our teams committed elsewhere, we are not in a position to step in and provide security for the conference.”
A Labour party spokeswoman declined to comment.