The bookmaker is investigating wagers from 42 gambling accounts with alleged links to BBC staff and Love Productions, the company behind the hit series, according to the Sun.
A total of 529 bets - potentially worth about £10,000 - were placed through the accounts that were created ahead of the pre-recorded final, which airs on BBC One on Wednesday, the newspaper reported.
A Ladbrokes spokesman said: “We flagged at the start of the series that we thought something smelled a bit strange. We are looking into it further.
“If we feel we’ve had the equivalent of a custard pie thrown in our faces we will think twice about whether we should bet on markets like this again in the future.”
A BBC spokesman said: “We have no knowledge of these claims and have asked The Sun to provide us with details to be able to look into it. We are still waiting.”
Bets placed on the outcome of television events such as the Great British Bake Off are often restricted to £20 at any one time, but punters are able to bet more than once over a period of days.
Wednesday’s final will see contestants Ian Cumming, Nadiya Hussain and Tamal Ray battle it out for the Bake Off crown.
Bets on this year’s final were suspended in August amid fears the winner’s name had been leaked.
Ladbrokes announced it had stopped taking wagers after it noticed suspicious play on one contestant, whose odds started at 12/1 and were reduced to 6/1, 3/1 and then evens.
Several of the wagers were the maximum the bookies would take for the show, and 90% were placed on one contestant.
A spokeswoman for Love Productions said: “Everyone who works on the production of the Bake Off series is bound by confidentiality. We take any allegation of breach extremely seriously, although we have not been presented with any evidence to support such a claim.
“We are surprised that Ladbrokes chose to take bets on a series which they know to have been pre-recorded.”