Canada's controversial gun registry is costing taxpayers far more than previously reported, CBC News has learned.

Nearly $2 billion has either been spent on or committed to the federal program since it was introduced in the mid-1990s, according to documents obtained by Zone Libre of CBC's French news service.

The figure is roughly twice as much as an official government estimate that caused an uproar across the country.

The gun registry was originally supposed to cost less than $2 million. In December 2002, Auditor General Sheila Fraser revealed that the program would run up bills of at least $1 billion by 2005.

But the calculations remained incomplete, so CBC News obtained documents through the Access to Information Act and crunched the numbers.

A large part of the $2 billion expense is a computer system that's supposed to track registered guns, according to one document. Officials initially estimated it would cost about $1 million. Expenses now hover close to $750 million and the electronic system is still not fully operational.

Other errors and unforeseen expenses include $8 million in refunds to people who registered their guns, and millions more in legal fees that mounted during court challenges.

A spokesperson for the Coalition for Gun Control disputed Zone Libre's calculations, calling the $2 billion figure inaccurate.

The auditor general has pledged to re-examine the gun registry to come up with an updated assessment. Last month, Prime Minister Paul Martin rejected calls to scrap the program. But he said the government intends to review the way it's being run and is prepared to make changes.

Former Justice Minister Anne McLellan declined to talk to the CBC about the gun registry during the investigation. Bill Baker, the head of the Canadian Firearms Centre, also refused comment.