The agency had requested a stay on Canada's competition tribunal's decision last week to approve the deal that would create the country's second-largest telecom firm.

At least two analysts downgraded Shaw after the court's stay order, citing worries that the deal would not close on its slated Jan. 31 date.

"It is uncertain if the appeal will be heard. If it is heard, then the outcome of the Rogers/Shaw transaction could be months away," said David McFadgen, analyst at Cormark Securities.

Shares of Shaw were trading 1.3% lower at C$38.5, below the offer price of C$40.50.

($1 = 1.3666 Canadian dollars)

(Reporting by Tiyashi Datta and Nivedita Balu in Bengaluru)