The Scot took over at Old Trafford from Sir Alex Ferguson last summer, and has struggled with his Premier League-winning squad.
After missing out on a number of transfer targets last year, United have made a woeful start to the season so far, and are currently looking odds on to finish outside of the top four.
A vast spend in the coming transfer window has been mooted, with a number of top – and expensive – stars said to be on their wish list.
Allardyce – who has also endured a difficult season with the Hammers – believes that Moyes might have to blow as much as £200m to repair his team:
“David is left with having to make more decisions about players at the end of the season than he expected. It looks like he will have to plan a rebuild and for a club like United, that could mean an outlay of £200million.” He wrote in his column for the London Evening Standard.
“As a manager, it is almost expected that your first rebuild is when you come into a club unless you inherit, ironically, as good a squad as Roberto Martinez has at Everton. Then it’s about reaffirming your position and doing as well as the manager you have succeeded.
“The hard bit, even if you are United, is finding the players. They didn’t do that last summer and that’s probably one of things David now regrets.”