Jackson was due to hold the reins for three matches as Town searched for a new boss following Graham Turner's resignation last Tuesday.
But he will now remain in the role at least until the trip to Notts County on February 22.
His first match at the helm saw Shrews fall to a 3-1 defeat at Swindon last weekend before the club's scheduled midweek trip to Colchester fell victim to a waterlogged pitch.
Former defender Jackson, who has been on the coaching staff since retiring as a player in 2010, has stated his interest in the position on a full-time basis.
And chairman Roland Wycherley, charged with making the new appointment, has now given him an extended period in which to prove his worth.
Shrewsbury are currently 22nd in League One and just one point from safety.