King has been struggling with a chronic knee problem in recent years.
Allardyce said: “Arguably, Ledley is in better form that Ferdinand and Terry and he’s in the squad because he’s a brilliant footballer.
“Harry Redknapp was saying Spurs wouldn’t get into the Champions League because their run-in against Arsenal, Chelsea, Manchester United and Manchester City was too difficult.
“But Ledley played in all those matches in and it was him who got Tottenham through those games even though he’s not fit enough to train.
“Arguably, he is in better form than Ferdinand and Terry. If he was fit enough I would expect him to start regularly for England.”
“On top form, the back four – even without Rio – is one of the best in the world,” he continued.
“The basis of England’s success or otherwise will come down to how they defend. If they concede less than anyone else then I think they’ll get to the final.
“There are doubts about Glen Johnson defensively, but from an attacking point of view, he is a fantastic player. David James will start as first choice in goal because for me the other two goalkeepers don’t have enough experience.
“That’s why I was so upset by Paul Robinson not going, not just as a manager, but also as an England supporter. I felt it was a mistake.”
