Canadian device vendor Research In Motion (RIM) has warned shareholders that it has a large inventory of Playbook tablets sitting in its channels at the moment, amounting to a provision for this quarter of around $360m.

Speaking at the end of last week, Mike Lazaridis, co-CEO of RIM, said that “an increase in promotional activity is required to drive sell-through to end customers.” Not an enviable position to be in during what is traditionally the most lucrative quarter of the year.

RIM said it sold approximately 150,000 PlayBook tablets into the channel in the third quarter and believes sell-through to end customers was higher than this amount. Yet the company isn’t shifting its stock as fast as it would like.

“RIM is committed to the BlackBerry PlayBook and believes the tablet market is still in its infancy. Although a number of factors have led to the need for an inventory provision in the third quarter, we believe the PlayBook, which will be further enhanced with the upcoming PlayBook OS 2.0 software, is a compelling tablet for consumers that also offers unique security and manageability features for the enterprise,” said Lazaridis.

While the company is still in the process of finalising its third quarter financial results, it said it shipped approximately 14.1 million BlackBerry smartphones in the third quarter ended November 26.

A further charge of around $50m will also be levelled against company revues for this quarter, related to the recent service outage, meaning RIM will likely miss its targets.