Andy Cole inspired Blackburn to their third victory in four games to give Rovers a massive boost as Birmingham City slumped to their fifth match without a win.
A badly demoralised Birmingham slipped to their second successive heavy home defeat during which they have conceded seven goals without scoring themselves.
Birmingham also finished with ten men after Frenchman Christophe Dugarry was sent off after he received two yellow cards in the space of eight minutes for ungentlemanly conduct.
Cole, an astute second-half substitute, created the passes from which Barry Ferguson and Lucas Neill scored the two crucial opening goals in the space of two minutes midway through the second period.
It was a massive win for Blackburn who were well worth their success over a Birmingham side which is beginning to struggle.
Rovers boss, Graeme Souness, was often agitated with the untidy first half which was often reflected in Blackburn's performance before the arrival of the inspirational Cole.
Blackburn were far from happy in the early part of the game when twice in quick succession Dugarry flattened Craig Short and Vratislav Gresko.
Short was subsequently involved in a running battle with Dugarry which ended in the second half when the petulant Frenchman received his marching orders.
Dugarry picked up a 63rd minute booking and seven minutes later collected a second yellow card in another off the ball incident.
The North West club rarely threatened any real danger in the first half which was in sharp contrast to their runaway success in the second period when Paul Gallagher was a major threat.
But it was only after Cole took over from the lacklustre Dwight Yorke that Blackburn stepped up a gear to carve out a fine win which was generated by two goals in the space of two minutes.
Cole threaded a through pass to Barry Ferguson in the 65th minute to score a well taken goal and two minutes later Lucas Neill latched on to a perfectly weighted pass from the former England star to notch the second goal.
Birmingham then capitulated when down to ten men with Tugay lashing in a 25-yard blockbuster in the 81st minute with the talented Gallagher taking a pass from Ferguson to slip his shot past a bemused Maik Taylor three minutes from time.
Afterwards Souness said: "We have been playing well without getting the results. Against Birmingham we turned on some great attacking play to pick up a fine win." Steve Bruce, Birmingham's manager said: "I can only apologise to Birmingham's fans. Until their opening goal we were well in the game, but after the sending-off of Dugarry we fell to pieces."