SAM Allardyce fears Wanderers will struggle to stay in the top half of the Premiership, if they fail to get their defensive house in order.

Although they remained fourth, there were alarm bells ringing as the Whites squandered a winning opportunity against Birmingham City on Saturday.

They paid a heavy price for failing to ram home their first half advantage but it was the defensive department that bore the brunt of the manager's criticism after Birmingham recovered to draw 1-1.

Allardyce described the defending as "schoolboy" and "comic" and warned: "If we are not going to get those clean sheets -- like Chelsea did, like Manchester United did and like Arsenal did on Saturday -- then we're not going to stay in the top half, we're going to plummet below half way because you can't keep asking the players to score two goals to win a Premiership match."

Despite beating Liverpool and drawing with Manchester United and Arsenal, Allardyce desperately wanted a victory over Birmingham to make a "statement" to his Premiership rivals that Wanderers are a true force to be reckoned with, especially at home.

But he had to settle for a point and, although Wanderers stretched their unbeaten run to six league and cup games, he assessed the performance as a let-down, adding: "If we are going to be any good and finish where we finished last year, this was the ideal opportunity to tell everybody what we are about, playing at the Reebok.

"When we have teams on the rack, we should finish them off. But we know we let everybody down and, more importantly, let ourselves down by not finishing Birmingham off."

TV replays suggested Wanderers had what could have been the winning goal disallowed in the 55th minute when top scorer Henrik Pedersen was flagged offside, and Allardyce had harsh words for the referee's assistant.

But he focused on the sloppy defending early in the second half that allowed Muzzy Izzet to cancel out Radhi Jaidi's 16th-minute goal, when he said: "It was a really bad decision by the assistant referee, but I would still have been very disappointed had we won the game because of what we did in the second half and how we conceded that goal."