For every one game sold at retail four are pirated, the UK's game publisher organisation claims.
The estimate is based on information received from "a number of publishers", UK Interactive Entertainment told Eurogamer sister site GamesIndustry.biz.
It was attempting to clarify a BBC report which claimed people who play illegal copies of videogames on chipped or modified consoles cost at least £1.45 billion in lost sales in 2010.
UKIE failed to reveal which console formats were included in its estimates, or whether PC games were included.
"We took a conservative position of saying if this is only 1:1 across all titles it would have a retail equivalent value of £1.45 billion. We did not say this was the loss to industry," Rawlinson said.
"What is clear is people who 'share' games via P2P networks or buy illegal copies are not buying the real product, and this reduces retailer sales. It can provide the consumer with a sub-standard product and money paid to illegal traders does not flow back to the creative.
"In turn, investors see higher risks/lower returns, and this in turn will undermine confidence in the sector and lower the amount of money invested, reducing the developer's chance to create new products." UKIE plans to commission research to look at issues involved in game piracy in an attempt to better calculate the damage.
Last year The Witcher 2 developer CD Projekt told Eurogamer digital rights management treats gamers like "criminals".
It "doesn't work", CEO and co-founder Marcin Iwiński said.
"Let's look at Call of Duty. We are frequently checking the torrent sites before making our decisions. The game is out a few days and you have 100,000 people downloading it simultaneously. So it doesn't work.
Piracy is clearly a big issue for CD Projekt – it's looking to get law firms to send letters threatening fines to those who pirate the game.
"Of course we're not happy when people are pirating our games, so we are signing with legal firms and torrent sneaking companies," added Iwiński.
"In quite a few big countries, when people are downloading it illegally they can expect a letter from a legal firm saying, 'Hey, you downloaded it illegally and right now you have to pay a fine.'
"We are totally fair, but if you decide you will not buy it legally there is a chance you'll get a letter.
"We are talking about it right now."