Woolwich Ferry workers plan to take strike action, affecting the cross-river service for 12 Fridays right into spring.

The Unite union said 88% of its 36 members voted for action which begins with a 24-hour strike on Friday, January 27, and will continue every Friday until April 14. They are protesting about what they claim is a failure to stick to agreements, health and safety worries and a culture of bullying and sexual harassment.

Briggs Marine Contractors Ltd , which operates the service on behalf of TfL denies the claims.

More than 3,500 car journeys as well as foot passengers and cyclists rely on the ferry each day. It is particularly popular with lorry drivers who are height-restricted by the Blackwall Tunnel.

Unite regional officer Onay Kasab said: “There is a very unpleasant culture of bullying and harassment at this company, including serious allegations of a sexual nature made by one of our female members.

“The large majority for 12 days of strike action underpins our members’ anger at the company culture.

“We accept that the strikes will cause serious disruption. However, the ball is very much in the court [of Briggs]. The bosses need to address these serious allegations urgently, if strike action is to be averted.

A spokeswoman from Briggs Marine said: “We do not recognise the issues set out in Unite’s statement and we have again requested talks with the unions to seek resolution. Most importantly, we will do everything we can to avoid inconvenience to the public.”

A TfL spokesman said: “We urge Briggs Marine and Unite and GMB to resolve this dispute as quickly as possible to avoid any disruption for Londoners.”