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Crossrail, the South-East's ^15bn new rail line, is on course for a humiliating signalling failure when it opens in 2018.

The project chairman, Terry Morgan, confirmed that a "mitigation plan" was being put in place as it grows increasingly likely that signalling on the 73-mile Berkshire-to-Essex link won't work properly. This would mean a reduction of train services from the start.

Crossrail uses a complicated mix of traditional metro signalling and state-of-the-art systems to link trains on the 26 miles of new tracks beneath London to existing major cross-country rail lines.

Engineers and rail experts are struggling to create "interfaces", meaning the trains are unable to smoothly switch from the relatively conventional Metro system to a higher-tech standard once they have left central London. Sources say with only three years to go these problems might not be resolved in time.