Bidders will ask for extra money to cover public relations implications of late delivery of Olympic work.

Contractors intend to charge more for work on the 2012 Olympic Games in London to take into account uncertainty over procurement plans and the public relations implications of delivering work late, it has emerged.

QSs and contractor sources said firms bidding for venues would ask for extra money because of fears of squabbles with subcontractors, design changes, labour shortages and the absolute deadline for completing work.

Developers are also understood to be in talks with contractors to ensure that they do not lose construction teams to work on the Olympics.

Andrew Dewick, joint managing director of London cost management at QS Northcroft, said that the most likely labour shortages would be among fit-out workers such as electrical.

He added, however, that pricing was more likely to be affected by other concerns, including media scrutiny and the political importance of such a high-profile public project.

Dewick said: "Contractors will price it generously. It has less to do with labour costs - they will just be very nervous about the risks."

Richard Steer, senior partner at Gleeds, described the project as "like a big Wembley" and said: "It's prudent [for contractors] to allow for any difficulties with the project and main contractors don't want to be held to ransom by their subcontractors." He added that contractors could only guess at the level of any premium that they charged, as under cartel law it would be illegal discuss tender prices.

Stephen Barker, a senior partner at RLF, a property consultant, said that the procurement path would dictate the level of increases.