The pills were found in the cover of the 18-certificate game
Four ecstasy pills have been found inside a computer game bought at a High Street store.
Richard Thornhill, 34, found the drugs under the front cover of X-Box game Grand Theft Auto IV, which he bought from Gamestation in Cheltenham.
Mr Thornhill said: "What made me feel the most distraught was the fact we let our 12-year-old play the game."
A spokesman for Gamestation said the company has launched an investigation and was assisting a police inquiry.
But the Thornhills claim Gamestation's initial response was to tell them to "flush the drugs down the toilet".
Mr Thornhill said he bought a second hand, or pre-owned, copy of the 18-certificate game before making the discovery last Sunday.
He said: "I was going to put it away and I felt a lump on the front cover.
"Inside the instruction booklet was a ball of Shrinkwrap, or Clingfilm. I thought it was just a ball of clingfilm, but then I realised there were tablets inside. I instantly felt sick.
"They had Mitsubishi signs on them, which I recalled meant they were ecstasy pills. I wasn't 100% sure though, so I checked online and sure enough I was right - it was ecstasy."
His wife, Lesley, contacted Gamestation's area manager whom she claimed invited her to hand the drugs over to the company so they could destroy them.
But the couple contacted Gloucestershire Police and officers collected the pills.
A Gamestation spokesman said: "We have rigorous procedures for accepting pre-owned titles and checking them before they are put back on sale.
"We have launched an investigation and will work closely with Cheltenham police to find out what happened."