The majority of London’s bus workers have gone on strike today in protest at their employers’ refusal to grant them an Olympic working bonus.

The move comes despite a court injunction barring staff at three bus operators from walking out, and an eleventh hour intervention by London mayor Boris Johnson.

Members of the Unite union are seeking a £500 bonus for working during the Games, plus £100 for each day they strike.

The union says that bus workers will see a “massive increase” in workload this summer, and are now the only transport group not to receive an incentive payment for London 2012, after rail staff secured bonuses ranging from £500 to £2,500.

London Mayor Boris Johnson called the strike “extremely frustrating” and accused Unite of using it as “a political tool.”

He ended his silence over the issue earlier this week by calling on bus companies to negotiate with the union, after he secured £8.3 million from the Olympic Delivery Authority in part-payment of bus driver bonuses.

Employers are said to have tabled a £500 offer for 80 per cent of the workforce, but negotiation talks between Unite and the bus companies broke down yesterday, paving the way for today’s strike.

Transport for London said that a third of bus routes were running this morning but “many routes were disrupted”.

There are more than 8,000 buses and 70 depots in the capital. Unite said that pickets had been set up and the strike was “well supported” by workers at the 17 bus operators involved in the one-day stoppage.

However, union members at Arriva, Metroline and Go Ahead have been prevented from joining the walkout after the firms won a last minute injunction against the strike action.

Unite has vowed to appeal the ruling, which it says “was given without any proper explanation”.