Newcastle United 0 Manchester City 2
Manchester City became the latest team to pile the agony on the under-pressure boss as the Magpies slipped to a third successive defeat.
The win takes City into fourth place, ahead of Liverpool, as they enjoyed their first away win since their opening day 2-0 success at West Ham.
But there was no denying that City fully deserved their first double over Newcastle for more than 40 years with goals in each half from Elano and Gelson Fernandes.
Elano's strike after 38 minutes meant that Newcastle had conceded the opening goal at St. James' Park for the sixth successive home game.
Yet it had all started brightly for the home side as Habib Beye had an early close-range header cleared off the line.
In fact, Newcastle had plenty of the play and possession but lacked the necessary killer punch in front of goal.
A mistake by Claudio Cacapa let in Stephen Ireland but he wasted a great opportunity to put City ahead.
Newcastle hit back with a couple of stinging shots from Obafemi Martins and Abdoulaye Diagne-Faye that were both well handled by Joe Hart.
Elano flashed a drive from the left that Shay Given did well to turn over the top, but the Brazilian was to make a later impact.
That came after 38 minutes when there was a clever one-two with Darius Vassell before curling a left-footed shot beyond Given.
Allardyce hauled off the woeful Martins at half-time and replaced him with Michael Owen, who almost scored within 20 seconds.
A defence-splitting pass from Charles N'Zogbia saw Owen latch on to the ball only to see his effort strike the right knee of Hart and flash behind.
But that was a rare scoring opportunity for Newcastle as City dictated the game and a double substitution by Sven-Goran Eriksson paid dividends.
It came after 76 minutes when Kelvin Etuhu cleverly held up a ball into the area from Vedran Corluka, who showed great awareness before picking out fellow substitute Fernandes.
He in turn finished superbly for his first Premier League goal just 40 seconds after running onto the pitch.
That goal signalled the end for Newcastle, who have now lost seven of their last 12 league games and, over the four festive period matches, have now picked up just one point.