The prospect of the Labour Party cancelling its annual conference has become ever more realistic after G4S turned down a last-minute offer to provide security. G4S has been present at the event for 20 years, but has recently been criticised by party figures for various prison contracts and links to Israel.

A replacement was found for the Liverpool event, a new security firm called Showsec, but they as yet are unable to settle an industrial dispute with the party over union membership for its workers. There have been threats to form a picket line outside the conference entrance, which several Labour members have said they would refuse to cross.

Merseyside police have said that the event cannot go ahead without security, and that they are not in a position to provide it. No other security firm has put forward a bid to police the conference in Liverpool.

In a statement the managing director for events in the UK at G4S, Eric Alexander, said: "This is a large, complex event, which we would ordinarily plan up to a year in advance.

"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.

"Our team of more than 100 security staff has secured the Labour Party’s annual conference for over 20 years and the feedback from officials and the police on our work last year, as in the past, was extremely positive.

"Clearly we were disappointed not to continue such a successful working relationship. 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 spokesperson said: “We don’t comment on commercial arrangements”.

The party voted to boycott G4S, who provide countless outsourced services to government departments, but who achieved notoriety in the build up to the London Olympics for failing to provide required security for the games. Jeremy Corbyn has criticised the company, which has a number of contracts in Israel.