OTTAWA - The Conservative party's public attacks on the CBC have been "wilfully destructive" and undermine its independence, says a newly uncovered letter to Prime Minister Stephen Harper from the broadcaster's Tory-appointed former chair.

The sharply worded 2010 letter, released last month under the Access to Information Act, alleges that unwarranted attacks that year "disparaged the Crown Corporation in order to solicit political donations for the Conservative Party."

The missive from then-CBC chair Tim Casgrain warns the party and government MPs against "intruding" on the broadcaster's independence as they seek "to influence the content of programming."

"While this may be fair game in partisan politics, the charges are unfounded in fact and wilfully destructive of an asset of the Crown."

Casgrain's dyspeptic dispatch was triggered by controversy over remarks by CBC pollster Frank Graves of Ekos Research to a newspaper columnist, Lawrence Martin of the Globe and Mail.

Graves later apologized for telling Martin he had urged the Liberal party to "invoke a culture war" with the Conservatives and to not fear polarizing debate over issues such as tolerance.

Conservative MPs and party officials immediately seized on the remarks, demanding the CBC fire Graves as its pollster.

Casgrain, appointed by the Harper government to the CBC board of directors in April 2007, said Graves' polling work for CBC had integrity and reliability — and noted the government itself had hired him in the past.

"The government comes dangerously close to intruding on the independence of the broadcaster when it seeks to influence the content of programming or determine whose views will or will not be represented on its airwaves," says the letter, a highly unusual direct communication from the CBC board to a prime minister.

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Casgrain's five-year CBC term ended in June 2012. An executive at a Toronto flight business, his only comment this week was that "the letter speaks for itself. I have nothing to add."

A spokeswoman for the CBC said the Prime Minister's Office never responded to the letter, which was also copied to then-heritage minister, James Moore, who also did not respond.

France Belisle said the chair and board have not sent any further letters to the prime minister touching on the public broadcaster's independence.

Harper's spokesman Jason MacDonald said the Prime Minister's Office has "no intention of getting into a play-by-play around correspondence that goes back to 2010."

"The CBC chair is entitled to his views and to expressing them. The government respects the CBC's independence, and it continues to receive significant taxpayer funds."

A spokesman for the Conservative party took issue with the Casgrain letter, saying this week that "no media organization, not even the CBC, gets to dictate how the Conservative party can and cannot fundraise."

"When the CBC invites partisan guests and treats them like neutral observers, we're going to point out their bias to Canadians," Cory Hann said in an email.

"When the CBC is being biased against our party in their 'news' coverage, we will never hesitate to inform Canadians."

An Elections Canada database indicates a Tim Casgrain twice donated $1,050 to Toronto's Eglinton-Lawrence Conservative Association in 2007 and 2008. The riding was then held by a Liberal but was won by Conservative Joe Oliver, now finance minister, in the 2011 election.

A recent fundraising letter from the Conservative party accuses a cartel of five big media groups in Canada of bias in favour of Liberal Leader Justin Trudeau, and pointedly asks party supporters whether the CBC should be privatized.

The 2012 federal budget chopped the CBC's budget by $115 million over three years, with the corporation shedding more than 600 jobs this year alone. The cuts were among a spate of spending reductions across government to balance the budget by 2015, and leave the CBC with just over $900 million in annual funding.

— With files from Steve Rennie

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