The government has claimed a new shopping centre in Croydon as evidence of the Olympic 'legacy'.
The arrival of Westfield in the South London borough was included in its study that said the games gave a £10bn boost to the UK economy.
According to the government, the £1bn investment would not have happened without London 2012 - so it was asdded into their report.
It also credited the Olympics with a £1.2bn in the Royal Albert Docks by a Chinese developer, and a £700m development in Battersea.
Experts said many of the investments included would have happened anyway.
But Vince Cable, the Business Secretary, defended the study.
He said: "The analysis that was done on inward investment involved actually talking to the companies who were making inward investment and asking the very simple question 'Would you have invested otherwise?'
"The answer we've had with a lot of the high-profile investment - like the Malaysians in Battersea Power Station - is that a lot of the key negotiations and support came out of the events that we organised around the Olympics.
"Would this have happened anyway? Some of these activities clearly would, but the Olympics were a key catalyst in making those investment decisions real."
Cable insisted said companies which had been considering investing in this country were persuaded to do so as a direct result of the Olympics.
He added: "I was one of the people who was very sceptical about the whole thing. I think I spoke against the Olympic Games when we put our bid in originally, because I thought it would be a big cost and there would be no benefit.
"What happened around the Olympics was an enormous amount of effort put in by my department and other ministers to try to attract big inward investment here, to try to support British businesses to get business on the back of it. It was done in a very sustained systematic way and it continues.
"This is a positive over and above the 'party', and I think it is very real."
The national policy chairman of the Federation of Small Businesses, Mike Cherry, questioned whether the Olympic effect was felt outside London.
Cherry told the BBC: "Out in the regions, we found that the effect of the Olympics and Paralympics, and the contracts we were expecting, really didn't materialise as much as I suspect many people were hoping for.
"A lot of work went into it at the very beginning, when it was all announced. But although some businesses certainly got some really good contracts, for the vast majority it just didn't happen."