The London Olympics will give a short-term boost to Britain's weak economy but economists predict the greatest sporting spectacle on Earth will fail to prevent a sharp slowdown this year.

The government has invested a total of 9.3 billion ($14.8 billion, 11.2 billion euros) to stage the Games, more than four times the original estimate when London was named host city in 2005.

"The Olympics is unlikely to prevent the UK's economic recovery from slowing again later this year as a result of further fiscal austerity, a weakening labor market and renewed recession in the eurozone," said Samuel Tombs, an analyst at Capital Economics research group.