Allardyce has issued a hands-off warning on Tomkins to Newcastle United.
Allardyce said: "We have never been in a position to sell anybody and we don't want to. We want to increase the size of the squad not decrease it and sell anybody.
"But you never know what happens in this window because if someone offers you an unbelievable amount of money for one of your players then the owners look at that and say that is too much to turn down, not that that has happened at the moment.
"But the most important thing for me is players coming, in not going out.
"We only have two centre-halves left James and (Winston) Reidy and we have a young 19-year-old at full-back because we have no one else, so I need two if I am really honest.
"I have been looking for a left-back for the last ten days and found that very difficult to find one to come and join us and now it is a left-back and a centre-half or a left-back who can play at centre-half ideally.
"On Monday, it will probably start with what's what, who's who, where's where and who wants to go here there and everywhere.
"There will probably be 50 to 60 calls between now and Monday to get somewhere to secure a player."