A trade union on Monday warned of more strikes at the UK's largest container port if pay demands are not met, threatening to cause further disruptions to the supply chain.

Workers at Felixstowe port in southeastern England began an eight-day strike over pay on Sunday, in the latest industrial action as decades-high inflation intensifies the country's cost-of-living crisis.

They say the pay offer they received does not keep up with inflation -- which has surged above 10 percent -- and includes a one-off lump sum payment.

"If we don't achieve what we're trying to achieve, there will be more strikes," Robert Morton, national officer for the Unite union, told Sky News.

"We've been asking for a minimum of the rate of inflation," Morton said.

Nearly 2,000 unionised employees at the port in eastern England, including crane drivers, machine operators and stevedores, are involved in the first strike at Felixstowe since 1989.

It comes amid stoppages over pay and working conditions across various UK industries, with railway workers just the latest to strike on Thursday and Saturday this week.

The strike comes after Covid and post-Brexit labour shortages have already hit the UK supply chain.

Morton said he accepted that further strikes at Felixstowe would mean "the supply chain will be severely disrupted", while saying the strike will end as soon as the port agrees to meet for negotiations.

The Port of Felixstowe said in a statement Friday that it was "disappointed" the walkout had gone ahead and called its offer of salary increases of on average eight percent "fair".

It said it "regrets the impact this action will have on UK supply chains".

Pal Davey, head of corporate affairs at the port, told Sky News on Monday that average pay at the port is "40 percent higher than national average" and workers had been given a "very fair offer".

"Our workers have been much better placed to weather the cost-of-living storm than the majority of workers in the rest of the country," he said.

Strike action over pay matching inflation is taking place in a wide range of sectors.

Even criminal lawyers who represent clients in court have launched strike action.

On Monday, their union, The Criminal Bar Association announced its members had voted to escalate their action and will stop taking on any new cases indefinitely from September 6.