LONDON — U.K. Olympic organizers run a risk of exceeding their $14.6 billion budget for hosting the 2012 London games and have little room left for unforeseen costs, Britain’s spending watchdog warned today.

The National Audit Office report concluded that while the venues are on time and largely complete, “not everything is rosy.” The report came as British Olympic officials announced that they had doubled the funding for security operations at venues, raising overall security costs for the 2012 Olympics to more than $1.6 billion.

“The government is confident that there is money available to meet known risks, but, in my view, the likelihood that the games can still be funded within the existing 9.3 billion-pound public sector funding package is so finely balanced that there is a real risk more money will be needed,” said Amyas Morse, the head of the National Audit Office.

If that’s the case, Olympic officials would be heading back hat in hand to British taxpayers who are already embroiled in tough economic times.

Britain’s National Audit Office examines public spending on behalf of Parliament.

Just hours before the report, Olympics minister Hugh Robertson told reporters at a news conference that the London Games remained financially on track — and within budget contingency planning despite the increased security costs. But the new security costs will certainly become a sensitive political issue.