Bechtel is furious that action by 600 workers, which is not backed by their union, has brought some of the work to a halt. Cliff Mumm, the Bechtel executive running the pounds 3bn line connecting central London with the Millennium Dome, warned the "illegal walkout cannot be allowed to continue".
And in his first intervention in the dispute, the Prime Minister declared that management should be allowed to do its job - a clear sign of how seriously the Government takes the issue.
A source close to the JLE project said: "The fact is that we need to get a productive workforce of electricians back on the job. This project has to be completed on time. Is the sense of urgency increasing daily? The answer is yes."
He said that in the "near term" the matter was one for Drake & Scull, the contractor, and the electricians to resolve. Asked whether Bechtel, which has staked its reputation on delivering the Jubilee Line to schedule, would resort to "scab" labour to break the strike, he said: "You can draw the conclusions you want to draw."
Drake & Scull has also run out of patience. Its project director, Chris Raven, told Construction News: "We will look at all the options open to us. At this stage we don't want to employ people who have to walk across picket lines. But bringing more staff on site is an option."
The prospect of an attempt to break the strike could see a return to the days of picket line clashes last seen outside Rupert Murdoch's printing plant in Wapping, east London.
Tony Blair has made a personal pledge to ensure the line opens on time. "It is not banging a few heads simply, it is making sure that the management is allowed to get on and do their job."
Tony Miller, a spokesman for the strikers, warned that electricians would "do everything possible" to prevent an alternative workforce crossing picket lines. He said employees had covered all entrances.
The electricians, who make up around half the workforce, would call for support throughout the union if management tried to break the strike, he said.
Mr Miller contended that the company had refused a number of proposals put forward by the men to end the dispute which is over the transfer of 12 electricians from London Bridge to the Green Park site.
The unofficial strikers argue that the men were being victimised for protesting about a deficient fire alarm system at London Bridge, although management argue there is no health and safety issue involved.
Mr Miller said Drake & Scull representatives were "aggressive and incompetent" and if there was any question of low productivity, it was the fault of "heavy-handed" management. The company was unavailable for comment.
Officials of the Amalgamated Engineering and Electrical Union are expected to address a mass meeting on Monday at which they will call on the men to return to work. Ken Jackson, leader of the union, said the organisation would do everything in its power to ensure that the line was completed on time.
London Underground (LU) is drawing up contingency plans that include taking people to the Dome by ferry. Glenda Jackson, the Transport minister, said yesterday it would be "irresponsible" not to have arrangements in place to cope with a "major failure of the Jubilee Line".
LU is working on alternative plans with London Transport Buses, London River Services, train operating companies, including the Docklands Light Railway, and London authorities. It believes it could bring the 35,000 people expected to visit the Dome each day just by using the first stretch of line, which runs from Stratford in east London to the Dome.
John Self, Jubilee Line general manager, said: "Once we have got Stratford to North Greenwich open, at least we have a credible route that would cater for the 35,000 people."
This section of the line should open in April, the second phase from the Dome to Waterloo in the summer and the final connection to the existing Jubilee line at Green Park in the autumn. London Underground has consistently refused to give even a month for the final opening.
The Government intervened in September after Tube bosses realised the line would not be open for the deadline of spring 1999. Bechtel was brought in as project manager and the final opening date was put back to "late Autumn" 1999, just weeks before the Dome opens.
LU chief executive, Denis Tunnicliffe, admitted this week that the strike, and "poor productivity" had put the project in jeopardy.Reuse content