Canada will be forced to play catch-up to its closest allies on a major international tax-evasion probe, after Thursday's revelation that Britain and Australia have had a huge trove of secret offshore financial records for years, while the Canada Revenue Agency has only recently requested access.

Revenue Minister Gail Shea has not explained why Canada wasn't a part of the three-country partnership announced yesterday that will be jointly investigating the records, believed to be largely the same leak of files obtained by CBC News through the Washington-based International Consortium of Investigative Journalists and revealed last month.

Britain, the United States and Australia said Thursday they have launched a joint effort to comb through the information and ferret out tax cheats. It could amount to the biggest ever international probe into tax evasion.

The British tax agency has had the information since late 2010, it confirmed to CBC News. It believes the 400-gigabyte dump of documents it received and shared with the U.S. and Australia to be "broadly similar" to the records obtained by the consortium of investigative journalists.

"All three countries have already identified a number of individuals who may have used complex offshore arrangements to commit tax fraud, and they are already under investigation," a spokesperson for Her Majestry's Revenue and Customs said in an email.

The Australian Tax Office, which got the records 18 months ago, has already red-flagged 65 people, launched audits against 35 and criminal investigations against two, citing the possibility of millions in evaded taxes by wealthy citizens.

Leaked records span 30 years

Canada has only just requested the files from Britain sometime in the last month, since the first wave of media reports on the data leak, Shea said in a statement late Thursday.

"I have reached out to the government of the United Kingdom and secured a commitment that information relevant to Canada stemming from this data will be shared," the statement said.

The statement cited the "close working relationship that Canada has developed with its international partners" but did not address why Canada was left out of the three-country tax-evasion investigation.

"Traditionally we have partnered with those very same countries on many cooperative measures in the past. So it is curious why Canada is not participating," said international tax expert Art Cockfield, a law professor at Queen's University in Kingston, Ont., who has consulted for the federal government.

"Why didn't they share this information with the Canadian authorities? Especially because there's at least several hundred Canadian taxpayers who have been identified in the documents."

The leaked records obtained by the International Consortium of Investigative Journalists contain information spanning 30 years and 10 offshore tax havens around the world, most notably the British Virgin Islands in the Caribbean and the Cook Islands in the South Pacific. It is believed to be one of the largest ever leaks of financial data.

The files shed light on more than 120,000 offshore entities — including shell corporations and legal structures known as trusts — involving 130,000 people in over 170 countries.

A worldwide media network has turned up revelations in the data on high-ranking politicians and their confidantes, including the prime minister of Georgia and the former president of Colombia; hardened criminals such as a cabal of Russians who stole $230 million from the country's treasury in a colossal tax fraud; and business tycoons.