This will make it compatible with the demands of English Premier League side West Ham United, who are planning to move into the Stadium in two years' time.

But, it is now claimed the cost will rise as a result of additional work required to strengthen the Stadium structure in order to bear the weight of the new roof, Sky Sports has reported.

This work, using technology previously only used on oil rigs, is taking longer than expected, and will have a knock-on effect on the timetable for other work.

The could take the overall cost for the Stadium over the £600 million ($960 million/€752 million) barrier, with the conversion having already cost £154 million ($247 million/€185 million).

The London Legacy Development Corporation, which is responsible for the work, remains confident any increase will be covered by savings elsewhere, but this is not likely to quell concerns over further escalations in the price and time-scale for the redevelopment.

"The Legacy Corporation and its contractors are working closely together to convert the stadium from its Games-time mode into a multi-use, year round venue," a statement from the Legacy Company said. 

"It is a highly complex scheme and subject to tight project management to ensure that all the risks and issues are properly managed, as would be expected on a fixed price contract and an undertaking of this scope and scale."

English Premier League side West Ham Utd are hoping to move from their current home at Upton Park in time for the 2016-2017 season ©Getty Images





This dispute marks the latest setback in a longstanding saga over the future of the stadium, which was initially designed as a largely temporary structure that would be removed after the Olympics, leaving the running track and just 25,000 seats.

But a decision was subsequently taken to convert the arena so it could be used for football, and, after a bitter bidding process West Ham United defeated Premier League rivals Tottenham Hotspur to be selected as the anchor tenant, with costs rising on several occasions as a result of the changed plans.

Andrew Boff, leader of the Conservative group in the Greater London Assembly, claimed cuts elsewhere must take place to compensate for the likely increase.

"The whole promise of the Olympics was to bring a legacy for London," he said.

"So if we are now saying that it is going to cost us £15 million more then it is less of the legacy, less of the housing that we need, less of the green space that we need as a result of this stupid roof they've decided to put on a Stadium that doesn't work for football or anything."

Before West Ham move in for the 2016-2017 football season, the Stadium is due to open for a Diamond League athletics meeting next summer before five Rugby World Cup matches are held there in the autumn.

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