The Town board took action following Friday evening's 4-1 defeat at Hartlepool United.
Speaking after the trip to the north-east, Downing took responsibility for the below-par performance.
"I put my team out and we conceded three goals in the second half again," he told the club's official website.
"I'm annoyed about it the same as everyone else because I'm in the thick of it, day in and day out.
"We try to get the right balance and the right selection but obviously over the last few matches that has not been the case.
"I'm scratching my head because we do the same routines and work religiously in training Monday to Friday but we have to produce it in the games."
Downing replaced John Ward in the Whaddon Road hot-seat when the former manager left to take over at Carlisle United in October 2007.