Dec 5 (Reuters) - The following are the top stories from selected Canadian newspapers. Reuters has not verified these stories and does not vouch for their accuracy.
* A trove of police wiretap evidence replete with allegations of extortion attempts, threats and boasts of numerous photographs of Toronto Mayor Rob Ford using illegal drugs is revealing the extent to which the mayor's behaviour exposed his public office to criminal elements. ()
* The government is blocking attempts to call on key figures in the Senate spending scandal to explain their role in the audit of Senator Mike Duffy's expenses. ()
Reports in the business section:
* The Bank of Canada says deep discounting by retailers is spreading disinflation - a byproduct of more consumers crossing the border to shop and the arrival here of U.S. chains such as Target Corp.
* National Bank of Canada continues to churn out solid profits from its core operations, but must iron out wrinkles created by one-time items. ()
* Toronto Mayor Rob Ford may have offered C$5,000 and a car to two men trying to sell a video of him smoking what appears to be crack cocaine seven weeks before the video was revealed in the media, according to newly revealed portions of a police document. ()
* John Thornton has laid out his vision for Barrick Gold Corp - a more diversified mining company that can tackle big projects by accessing capital and partners in Asia. ()
* CGI Group Inc appeared to weather the storm following a sizable sell-off in October related to its role in the troubled new U.S. health care insurance website, but the stock has fallen on hard times again after a solid run higher in November as questions resurface about the impact the botched site will have on the company's future prospects. ()