Relations between the two sides hit a new low on Friday when the company confirmed it was taking legal action in the US to defend itself against attempts by former port workers to stop shipping lines from using the Port of Liverpool.
So far the dispute has cost the company pounds 4m in lost profits and at one stage had wiped pounds 75m off its stock-market value.
The sacked men's shop stewards have received notice that Mersey Docks is seeking an injunction through the US National Labour Relations Board to prevent unlawful industrial action by secondary pickets at east coast ports in the US.
"It's a disgrace," said dockers' leader Jimmy Nolan. "They are trying to use US law to get at us when the UK government should step in." The Treasury is Mersey Docks biggest shareholder with a 13.9 per cent stake.
Last week, John Bowers, president of the International Longshoremen's Union of America, warned the Port of Liverpool that it could lose ACL, the biggest single user of Liverpool's container terminal, unless it reopened talks with the sacked workers.
ACL had threatened to leave Liverpool in the early stages of the dispute. The deadline for withdrawal passed without incident, but the ultimatum is said to have led to the first direct talks between the two sides just over a week ago.
A spokesman for Mersey Docks said the action was being pursued in the US because British courts had no direct jurisdiction over situations arising there.
"The dismissed men continue to try to prompt action in ports overseas that is intended to damage the Port of Liverpool and destroy jobs it supports," he said.
The dockers, who are seeking legal advice, have received support from 22 countries, aimed at bringing Mersey Docks to the negotiating table by boycotting ships whose owners use Liverpool.
The dismissed dockers recently rejected an pounds 8m settlement - worth up to pounds 25,000 per man - negotiated by Bill Morris, general-secretary of the TGWU trade union. The strikers are holding out for immediate reinstatement and the end to casual labour at the Port of Liverpool.