Network Rail tried to conceal engineering failures that led to long delays for thousands of passengers and more than 500 train cancellations.

An internal memo obtained by The Times reveals that Network Rail instructed its press officers to hide the truth from the media about the cause of the delays on the Great Eastern main line into Liverpool Street station in London on Tuesday morning.

The infrastructure company was under pressure to complete Easter engineering works on time after being fined £14 million for overruns that caused chaos on the West Coast Main Line and routes into Liverpool Street at new year.

Train companies and the Conservatives said that those problems exposed Network Rail’s lack of accountability. It was created by the Government to replace Railtrack and has neither shareholders nor competitors.

Errors by Network Rail engineers meant almost five hours’ delay in restoring services after Easter engineering works at Shenfield, in Essex. Thousands of commuters, including Sir Ian McAllister, the chairman of Network Rail, had to queue for buses and taxis or abandon their journeys.

Network Rail failed to test the signalling system in advance to ensure that, after switching it off during the works, it would operate properly when turned back on. Several signals were stuck on red.

National Express, the train company operating on the route, said that Network Rail’s work logbook showed errors in the new signalling design and faults in overhead power lines. But senior Network Rail executives claimed that the delays were caused by a points failure unrelated to the works.

Iain Coucher, Network Rail’s chief executive, who went to Liverpool Street to apologise in person to passengers, told the BBC on Tuesday lunchtime: “It wasn’t related to the engineering works we were doing over Easter.”

A Network Rail spokesman said: “The problem was unrelated and very coincidental.”

But the memo reveals that Network Rail press officers were instructed to give a more truthful account only if asked directly: “Is it related to Easter engineering works?” They were told that, at first, they should conceal the link by giving journalists the “line to take”. If pressed, they should admit a link by saying that “problems occurred when returning the entire signalling system for the area back online”.

Brian Cooke, the chairman of London TravelWatch, the passenger watchdog, said: “We are very concerned that Network Rail were being less than fully truthful on Tuesday, which led to even more confusion among the people who matter most: the passengers.”

National Express has complained to the Rail Regulator and asked for an investigation into Network Rail’s conduct.

The company sent a briefing, disputing Network Rail’s version of events, to Ruth Kelly, the Transport Secretary, who yesterday was having a prearranged meeting with Mr Coucher.

It said: “The problems with the signal design resulted in nine signals and two sets of points being out of use for the entire day. The impact on the train service was 7,590 minutes delay, 347 full cancellations, 182 part-cancellations and [train punctuality] for the day of 55 per cent.”

In a statement last night, Network Rail said: “We’ve been completely up-front about the cause of the disruption yesterday. It was a failure of our infrastructure and we’ve said so. This is nit-picking as far as passengers are concerned, as they expect the industry to work together to run trains on time.

“We apologise to passengers for the problems they experienced yesterday and we will work very hard to make sure that they do not have to go through this again.”

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