London’s bus staff are to stage two further walkouts in their efforts to secure a bonus for working during this summer’s Olympics.

Members of the Unite union working at the capital’s 70 bus depots are to strike next Thursday 5 July and then on Tuesday 24 July – just days before the opening ceremony of London 2012.

The move follows a 24-hour strike last Friday, which saw only a third of the capital’s bus routes running.

The union is asking for a £500 incentive payment – plus £100 for each strike day – for London’s 24,000 bus workers, who they say will have a “massive increase in workload” this summer.

They have so far failed to negotiate a deal with the capital’s 20 private bus operators, despite London mayor Boris Johnson stepping in to secure £8.3 million from the Olympic Delivery Authority to go some way to cover the total bonus cost.

Unite says that the bus companies are refusing to join Acas talks, and accused the employers of playing a “dangerous game of brinkmanship” with less than one month to go before the start of the Games.

Unite regional secretary, Peter Kavanagh, said: “Unite will be at Acas next Monday ready to meet with the bus operators. This dispute could be resolved at a stroke if the operators negotiate meaningfully.”

Rail and tube workers have already brokered Olympic payments ranging from £500 up to £2,500, and bus workers are now the only major group of transport staff not receive such an award.

News yesterday that employees of London’s bike hire scheme have also secured a £500 payment has strengthened Unite’s call for a bonus.

“Even ‘Boris bike’ workers are getting a £500 Olympic award,” continued Kavanagh. “There is no justification to ignoring the massive increase in workload bus workers face. They will be on the front-line, keeping London moving during the Games.”

But Leon Daniels, Transport for London’s managing director of surface transport, said that Unite had failed to put any offers – which included a £500 bonus for around 80 per cent of the workforce – to its membership.

He reiterated that it was not TfL’s responsibility to step in and attempt to settle the row.

“It is and always has been for the bus companies and Unite to resolve this dispute, and Londoners will doubtless agree that it is completely unnecessary for the Unite leadership to threaten further disruption,” Daniels said.

Unite also confirmed that it would re-ballot workers at three bus companies – Metroline, Arriva and Go Ahead – who had previously been forbidden to join last week’s strike action by a last-minute court injunction.