Three goals in six minutes have given Nottingham Forest a 3-0 half-time lead over the Blues at half-time at Portman Road, Nikola Milenkovic giving them the lead before Anthony Elanga netted twice.
Omari Hutchinson returned to an otherwise unchanged Town XI having been a sub at Crystal Palace last week.
The ex-Chelsea man came into the side as the number 10 with Julio Enciso on the left, Jaden Philogene again on the right and Jack Clarke dropping to the bench.
Forest were unchanged from the team which beat Manchester City 1-0 at the City Ground last week with former Blues loanee Chris Wood up front.
The visitors started on the front foot and on three Callum Hudson-Odoi worked his way into the area and would have been in on goal but for Jens Cajuste’s leg dispossessing him.
Town began to get more into it, however, and on four Hutchinson was tripped just outside the box to the right by Neco Williams. The England U21 international took the free-kick himself but hit the wall.
On 11, with the Blues seeing more of the ball than the Premier League’s tird-placed side, Leif Davis sent over a looping corner from the right and Liam Delap rose high at the back post but nodded into the Sir Alf Ramsey Stand.
A minute later, a Forest cross from the left was half-headed away by Davis at a stretch at the far post and Ola Aina scuffed his volley wide and into the North Stand.
In the 14th minute, Elliot Anderson gifted the ball to Delap not far outside the area after Forest had got into a mess after a throw on their right and the striker took it forward before being dispossessed. The loose ball fell to Julio Enciso and his shot deflected behind for a corner.
The flag-kick was played to Hutchinson on the edge of the box by Davis and the forward took a touch before hitting a curling left-footed effort which flew just over Matz Sels’s crossbar.
Town continued to see most of the ball with Forest halting their progress forward by giving away tactical free-kicks on a couple of occasions.
However, on 21, following a corner, Hudson-Odoi wafted a cross from the left to the far post and Nicolas Dominguez turned the ball into Alex Palmer’s arms from a very tight angle.
A minute later, Forest threatened again after Davis’s clearance from the edge of the area was deflected into the path of Anderson in space, but his shot struck Wood and cannoned wide when Town might otherwise have been in trouble.
There was an even bigger scare for the Blues on 25 when Hudson-Odoi, the visitors’ main threat, burst past Town stand-in skipper Dara O’Shea on the Town left and got to the byline. As O’Shea and Luke Woolfenden both slid in, Hudson-Odoi sent over a low ball which flew past the two Blues defenders, perhaps clipping one of them, behind Palmer and across the face of goal a couple of inches from the line but without anyone being able to add a touch.
Soon after, Kalvin Phillips went to the sidelines due to a bleeding foot while play continued before returning to the game.
Forest were by now well in control and looking more and more dangerous with most of their attacks going through Hudson-Odoi down their left flank.
On 33, Wood got between Woolfenden and O’Shea to nod down a Morgan Gibbs-White cross from the right, but too close to Palmer, who blocked before claiming.
But the travelling Forest support didn’t have to wait too much longer for a goal. In the 34th minute, Palmer came out of his box to clear into the stand, but the ball smashed off Jacob Greaves and behind for a corner on the visitors’ right.
The flag-kick was half-cleared to Hudson-Odoi on the left by Greaves, the England forward clipped a cross to the far post to Dominguez, Delap was only able to get a weak head on the Argentina international’s nod back and the ball fell to Nikola Milenkovic, who gleefully slammed home.
Two minutes later, it was 2-0. Hutchinson lost the ball in the centre circle, Anderson swept a pass wide to Anthony Elanga, who took it on towards the Town box and with Greaves standing off him, the former Manchester United youngster shot across Palmer and just inside the post.
And on 41, Elanga made it 3-0 with his second of the game. Milenkovic played a long ball from the back, Woolfenden and Wood battled without either getting the ball and Elanga nodded between and beyond O’Shea and Greaves before slipping it past Palmer.
Having been in the game, if on the back foot, at the half-hour mark, the shell-shocked Blues were suddenly all but out of it via three goals in six minutes, all of which Town should have defended much, much better.
As the half moved into two additional minutes, Phillips struck a shot which flew over Sels’s bar.
At the whistle, there were muted boos from some sections of Portman Road after another half which had begun promisingly but with the Blues going in at the break behind and on this occasion with the opposition having an unassailable lead.
As in the previous two games against Forest, the opening 20 minutes or so had been an even contest but as the half-hour approached, the visitors began to threaten more and they had had a couple of chances before the opening goal.
That goal seemed to rock the Blues, who collapsed in the manner they did in a similar spell before half-time against Manchester City earlier in the year.
There seems little hope that Town can get anything out of the match from here, while Wolves lead 1-0 at Southampton and the Blues seem set to end the day nine points plus goal difference from safety with only nine games to go.
Town: Palmer, O’Shea (c), Woolfenden, Greaves, Davis, Phillips, Cajuste, Hutchinson, Enciso, Philogene, Delap. Subs: Walton, Johnson, Burgess, Townsend, Morsy, Taylor, Broadhead, J Clarke, Hirst.
Forest: Sels, Aina, Milenkovic, Murillo, Williams, Anderson, Dominguez, Gibbs-White (c), Elanga, Hudson-Odoi, Wood. Subs: Hennessey, Morato, Sangare, Awoniyi, Moreno, Jota, Yates, Boly. Referee: Michael Salisbury (Preston). VAR: Jarred Gillett.