The RCMP says it has not yet been asked to investigate a day of wild trading in Taseko Mines stock that provoked suspicions insider information was leaked weeks before Ottawa rejected a proposed B.C. gold mine.

John Olsthoorn of the RCMP's integrated market enforcement branch confirmed Friday that the Mounties have not yet been asked to investigate the matter.

"The RCMP has not yet received a referral with respect to this matter," Olsthoorn said from Ottawa, adding that "the RCMP is not in the position to comment further on this specific matter at this time."

Vancouver-based Taseko Mines Ltd. (TSX:TKO) suffered a major setback earlier this month when its lead project, the Prosperity gold mine, failed to get federal environmental approval.

But a CBC news report has raised questions about unusually heavy trading in Taseko shares on Oct. 14 — about 2 1/2 weeks before the federal environment minister announced the mine did not get approval.

Taseko said it had no explanation for the precipitous Oct. 14 drop and the shares quickly bounced back. Following the announcement, Taseko's shares plummeted by 25 per cent.

Such fluctuations do happen occasionally among junior mining stocks but trading in Taseko was unusually heavy that day, with about 7.5 million shares exchanged in Toronto and nearly 23.5 million traded in New York.

Insider trading is difficult to prove — last year, just 16 illegal insider trading cases were concluded by regulators across the country, compared with eight the year before and seven in 2007.

The first Canadian to be convicted under federal laws that came into place in 2004, Toronto lawyer Stan Grmovsek, was sentenced in January to 39 months in prison for his role in a massive scheme that netted him and a friend about US$9 million — the largest prison sentence for such an offence in Canada.

Illegal insider trading carries a maximum prison sentence of 10 years and requires the Crown to proved that the accused "knowingly used insider information." Individuals may also be prosecuted under the Securities Act, which limits imprisonment to five years less and day and has a less onerous burden of proof.

Opposition MPs have called for an RCMP probe into whether there was a leak of information — perhaps from the Environment Ministry itself — ahead of the formal announcement.

MP Mark Holland, representing the Ontario riding of Ajax-Pickering, sent a letter to the RCMP requesting an investigation.

"As the integrity of the federal government and Cabinet is a matter of serious public concern, it is in the interest of all Canadians that this matter be resolved," Holland said Friday in his letter.

"I, therefore, request that you look into this case and determine whether or not there are grounds to launch a formal investigation."

For the latest from The Canadian Press, scroll down The Tyee's home page or click here.