LONDON (AFP) - Britain's government on Tuesday defended plans to let civil servants work from home during the London Olympics, insisting staff will not use it as an opportunity to shirk their normal duties.

From July 21 -- six days before the opening ceremony -- until the Paralympic closing ceremony on September 9, ministries will allow staff to work from home to avoid the widely anticipated bottlenecks on London's transport system.

But the policy has prompted criticism from at least one business group, who said it would lead to the government working only "intermittently" for seven weeks.

A spokesman for the Department of Transport stressed that working from home was just one of a range of "flexible working arrangements" available to civil servants.

"In some cases, working from home is an option, but it is only one option," the spokesman said.

"It is not appropriate for all staff. In every case, staff will be expected to work just as hard and for the same amount of hours as if they were in the office.

"We are encouraging staff to plan ahead and consider different work and travel patterns during the Games," he added.

"This might include walking or cycling, changing their route of travel to and from work or re-timing their working day to avoid the busiest periods."

But the Business Services Association, which represents service firms employing 500,000 people across Britain, said the policy would cause a drop in the government's workrate.

"Seven weeks is a long time to have the heart of government working intermittently," the BSA told Britain's Times newspaper.

"We would encourage ministers and Whitehall to apply themselves as energetically as the private sector is to driving the economy forward, Olympic Games or no Olympic Games."

Prime Minister David Cameron was forced to meet business leaders on Monday after senior ministers infuriated executives by telling them to stop "complaining" about the struggling economy and work harder.

Posters have appeared in recent weeks on the capital's Underground train network, advising all Londoners to consider working from home during the Olympics.

On the busiest days of the Olympics, the city's creaking transport system is expected to handle three million journeys a day more than usual, according to Games organisers.