Allsopp, best known for hosting 'Location, Location, Location', told the Huffington Post UK: "Like any intelligent person who is looking at the market as a whole, I have my reservations about that scheme. There are parts that will put people at risk."
The TV expert's warning comes as Bank of England governor Mark Carney told MPs he does not have the power to "turn off" the scheme, launched by the Chancellor, to offer state-backed mortgages to aspiring home-owners on properties worth up to £600,000.
Allsopp's concern about Osborne's scheme may be unexpected as the TV presenter, a Tory party supporter, campaigned with them before the election against rules to force house sellers to provide "home information packs" (Hips), which she branded an "idiotic piece of legislation".
Business Secretary Vince Cable and Treasury committee chair Andrew Tyrie have both expressed concerns that it could push up house prices and destabilize the market. Spiralling house prices in the capital has led Lib Dem MP Simon Hughes to warn that London property was becoming "a mere commodity for the global super-rich".
Mark Carney confirmed to Tyrie in a letter that the Bank of England's Financial Policy Committee (FPC) "does not have a veto on the scheme", but can make recommendations on its management.
Last month, George Osborne asked the FPC to annually review Help to Buy, starting from next September and also advise the Treasury in the event that it wishes to extend the scheme after its three year duration.
Tyrie wrote to Carney to clarify what powers the Bank had, after Deputy Prime Minister Nick Clegg told a newspaper that it could "turn off" the scheme.
The MP also quoted Tory party chair Grant Shapps, who told the BBC that the Bank of England was "solidly in charge" of Help to Buy and would prevent any "housing bubble".
Carney confirmed in his reply to Tyrie: "For the avoidance of doubt... the FPC has no power to require HMT (the Treasury) to vary the terms of, or close, the Help to Buy scheme.
"The FPC only has the authority to make recommendations in connection with such matters."
Tyrie praised Carney's letter as a "step forward", adding: "It brings some much-needed clarity to the Government's Help to Buy Scheme. We now know who is responsible for what. The Bank of England has no power of veto over Help to Buy. Responsibility for it lies with the Government."