In September, the programme relaunched as a one-hour format filmed in front of a studio audience, starting at 8pm rather than the usual 7.30pm.
Presenters Nicky Campbell and Julia Bradbury were also replaced by Rogue Traders' Matt Allwright and Anne Robinson, who returned to the show after an eight-year absence.
Despite reasonably strong early ratings for the new set-up, audience figures steadily declined as the series progressed. According to figures supplied by data firm Attentional, the series averaged 3.9m viewers compared to the 4.6m average when it was a half-hour format in 2008.
Watchdog was initially due to return for another series in the New Year, but the programme will now be delayed until spring while the format is fine-tuned.
However, a BBC spokesman told The Guardian that the show will be filmed live at BBC's Media Centre on Wood Lane, London when it returns. It will also be expanded from six to nine episodes.
He added: "The situation as it stands is that Watchdog will return in the spring as a live show, hence its return has been slightly delayed so the schedule can accommodate this."