Offering a rare peek behind the curtain at an ad revenue-challenged CTV, minority investor Torstar Corp. on Thursday said it has written down the value of its 20% stake in CTVglobemedia by a third.

‘All media assets have been badly affected by the sharp downturn in the economy and CTV enjoys no immunity from these forces,’ Torstar CEO Rob Prichard told analysts after the newspaper and book publisher posted its latest year-end results.

Prichard said the economic downturn has drastically sapped ad revenues at CTV, causing Torstar to record a $95.7-million write-down on its CTVgm investment to $200 million.

‘The write-down is a direct reflection of the economy in general and the challenges of conventional television in particular,’ he said.

Torstar in 2006 paid $376 million for the stake in CTVgm, which owns the CTV network, The Globe and Mail newspaper and assorted specialty channels and radio stations.

In 2007, during better times for Canadian TV, Torstar had a carrying value of $409.2 million for its CTVgm stake on its balance sheet.

Torstar said the non-cash charge for its minority stake reflects the impact on CTVgm ‘of lower estimated future cash flows in respect of certain of its television (in particular, conventional television), radio and print assets.’

Since BCE took CTV private in 2000, the broadcaster has not had to issue quarterly financial results. So the Torstar results offer a small window on CTV’s balance sheet aside from its expenditure reports to the CRTC.

Going forward, Torstar said CTVgm’s 2009 results ‘are expected to be negatively impacted by the reduction in advertising revenues in their television, radio and newspaper businesses.’

As it prepares for licence renewal hearings before the CRTC, CTVgm on Wednesday said it will shut down two conventional TV stations in Wingham and Windsor, ON, rather than renew their licences, as they have little hope of returning to profitability in the current business climate.