The "Stress Test" on Tuesday and Wednesday aims to replicate arrangements for the July 27-August 12 Games when companies are being told to encourage staff to work from home or stagger starting times to ease the strain on public transport.

"On the busiest days of London 2012, there are expected to be an extra three million journeys on the public transport system," said Mark Naysmith, Games readiness director at business advisory group Deloitte.

"It is essential that companies across the city, large and small, have thought through how their business and their people will cope with this period," he added.

London's transport authorities want to cut the number of commuters using public transport by 30 percent during the Games to help ensure the city's crowded trains can cope with the influx of visitors for the Games.

That means more remote working and variations to regular shift patterns to avoid peak times for congestion.

Once the Olympics are finished, London hosts the Paralympics from August 29 to September 9 - placing a fresh strain on its ageing transport network.

Britain's economy went back into recession in the first three months of 2012 and companies need to try to wring maximum value from the sporting summer, the third times London has staged the Olympics.

A report from ratings agency Moody's last week said that hosting the Games would give its economy and companies only a short-term boost.

The high-rise Canary Wharf financial district in London Docklands, where almost 100,000 people work, is only around three miles from the main Olympic park.

Deloitte, a sponsor of the London Games, is running the tests this week in coordination with Canary Wharf Group.

Thomson Reuters is joining the test on Wednesday and is encouraging many of its more than 5,000 London-based staff to participate. The company has its main London office in Canary Wharf and a technical centre nearby.

(Reporting by Keith Weir; Editing by Mark Potter)

• A Permanent Economic Emergency