"London's opening and closing ceremonies are a once-in-a-generation opportunity to showcase the very best of our country to four billion people around the world,'' Sports Minister Hugh Robertson told reporters.
"To get the ceremonies absolutely right and boost the Games' business and tourism legacy, we are putting additional investment into our ceremonies.''
The money is set to come from the public-funded Games purse rather than the organising committee's private budget, which sponsored the initial STG40 million, because it is the government which asked for the change.
Mr Robertson said only that the bulk of the money would be spent on "technical areas''.
Specifics of the ceremonies are yet to be revealed but rumours include performances by Take That, the Spice Girls and Beatles legends Sir Paul McCartney and Ringo Starr.
At the last Olympics in Beijing, the Chinese government spent some STG69 million on the opening ceremony alone, but Mr Robertson said Britain was not trying to compete with that.
"That's an arms race we won't win,'' he said.
"We had to look at what was available and realised that this was a great opportunity and we had to make the most of it. We decided to go in at the higher figure for the benefit of the country.''
- AAP