Workers are set to go on strike after an alleged four-year campaign of sexual harassment.
Travellers face disruption tomorrow due to the dispute, which also involves claims of a “bullying culture”.
About 95 per cent of the workforce are set to walk out after a member of staff made a formal complaint of sexual harassment.
The Unite union said this was among “a number of serious allegations” into which management “had failed to make sufficient progress”.
The Standard has learned that in December Tara Brackley, a secretary for Briggs Marine Contractors, which runs the service on behalf of Transport for London, claimed a member of staff had sexually harassed her for years.
She said her formal grievance was being handled “terribly”, and now her union is going on strike.
Briggs Marine said it was “disappointed” by the decision and “refutes the allegations of stalling being set out by Unite”.
Ms Brackley told union officials she had been keeping a dossier of the alleged misconduct since 2013, but had not raised it previously out of the fear of losing her job.
She told the Standard the man would regularly make lewd comments towards her. She said: “He constantly told me he loved me, that I looked attractive, blowing kisses, sneakily squeezing my shoulders, rubbing and stroking my neck, eyeing me up and down sexually, whispering in my ear, telling me we should run away together — it made me feel very, very uncomfortable. He would not stop even when I asked him to.”
He once rubbed his crotch in front of her, simulating sex, and attempted to playfight with her, she said.
Ms Brackley, 43, who has a long-term partner, said she was considering taking the matter to an employment tribunal. “It was just disgusting behaviour,” she said.
“This man intimidated me. They were all friends and I had no one in the office to turn to. The way the company has handled it has been awful.”
A friend said: “She would leave the office in tears. It was on an almost daily basis.”
Her complaint coincided with a breakdown in industrial relations between the union and the company over a number of other disputes, including alleged health and safety breaches.
The union said staff had been ordered to work in the hull of a boat where exhaust fumes were leaking, causing one worker to be hospitalised. It also claimed managers took “shortcuts” in fixing one of the lifeboats, which could have left it unusable.
Workers walked out this year before suspending action so talks could take place. About 80 staff were set to walk out on Tuesday but the strike was suspended to allow for more talks. A decision whether to proceed with tomorrow’s 24-hour strike will take place today.
Unite officer Onay Kasab, who called senior managers “intransigent, evasive and prone to stalling”, said enough progress had been made to suspend Tuesday’s action, including a management restructuring.
But he said: “Other issues remain, including investigating the case of alleged sexual harassment, and health and safety and allowances.” The GMB union is also involved.
The ferry, which links Woolwich and North Woolwich, carries about a million vehicles and more than two million passengers a year.
Briggs Marine said Unite had been “kept up to date with the progress of investigations”. It said: “We have been unwavering in our willingness to hold productive talks and to investigate the issues raised with us thoroughly and fairly.
“Our discussions with Unite and GMB continue and, if at all possible, we will avoid strike action. In terms of the specific issues being raised by Unite, these are currently under investigation and we are unable to comment.”
Leon Daniels, TfL’s director of surface transport, said Briggs Marine and the unions should “resolve this dispute as quickly as possible”.