A strike at Britain’s largest container port will escalate unless workers are given an improved pay offer, a trade union boss said as she signalled that disruption could continue until Christmas.

Sharon Graham, general secretary of the Unite trade union, addressed a flag-waving crowd of striking workers gathered on a roundabout near dock gate number one at the Port of Felixstowe in Suffolk.

Almost 2,000 dockers have walked out in a dispute over pay, and on the fourth day of an eight-day strike Ms Graham joined some of them on the picket line.

There was a festival atmosphere as music, including Fight For Your Right by Beastie Boys, was played through loudspeakers, and there were cheers when passing vehicles sounded their horns.

Ms Graham said that disruption at the port “is not necessary” and bosses “just need to pay the 10%” increase in wages that the union is requesting for workers.

She said the employer had made multi-million pound profits but were “asking these workers to take a pay cut”.

“It’s absolutely totally abhorrent,” said Ms Graham.

“At the moment the employer has not come back to the table with an improved offer and I’m here today to support these workers but also to say we will escalate this dispute unless they come back with a revised offer because this is ridiculous that they’re making this huge profit and they’re asking workers to take a pay cut.”

She said she is speaking to reps and stewards on Wednesday and they will “discuss what that escalation looks like”.

“They could give these workers a 50% pay rise and still be in profit, and we’re only asking for 10%,” she said.

“As far as I’m concerned this is laid at their door.”

Asked if disruption could continue until Christmas, she said: “I think in a sense that’s a question for the employer in some ways.”

But she continued: “Yes, obviously and unfortunately I have to say, if they don’t come back to the table this action will continue, and that’s not good for the public, it certainly isn’t good for these workers and I’d also say it’s not good for the employer.”

Engineer Stefan Long, who was among the striking workers, said: “If we can’t reach an agreement that’s worthwhile even balloting us as the members on, then it’ll go as far as it needs to go.

“People feel so strongly about this, it speaks for itself.”

The 33-year-old, who lives in Ipswich with his wife, said they have had to “readjust our lifestyle” as costs rise, with his energy bill soaring from £80 to £220 per month.

“We’re cutting back on everything, absolutely everything,” he said.

“You see the margins shrinking and I feel for those who’ve got husband, wife, two children, three children. How are they going to get by?

“How are they going to feed their children and heat their homes?”

A port spokesperson said: “A lot of our employees feel let down by Unite.

“Many want to work and are angry that they have not been allowed to vote on the latest company offer.

“Unite say they are a democratic union but their words don’t match their deeds and they are promoting a national agenda at the expense of many of our employees.

“The port has offered a deal worth 8.1% to 9.6% this year.

“The strike imposed on them by Unite is an effective pay cut of 2.2%.

“Many employees have told us they want to come to work but feel too uncomfortable to do so.”