Concerns were raised after the Government revised its initial target of 90% of the UK having superfast connections by 2015 to 95% by 2017.
The tender process also drew criticism when just two service providers - BT and Fujitsu - were named as approved bidders, with Fujitsu eventually dropping out.
The Public Accounts Committee (PAC) said the Department for Culture, Media and Sport (DCMS) mismanaged the project, and BT was exploiting its monopoly by restricting access to cost and roll-out information.
PAC chairwoman Margaret Hodge said: "The consumer is failing to get the benefits of healthy competition and BT will end up owning assets created from £1.2 billion of public money.
"Overall, BT is supposed to provide at least 90% coverage in rural areas but it is preventing local authorities from publishing proper information on the areas the company will and will not cover.
"Details of speed and coverage in each local project are also being kept confidential, preventing other suppliers from developing schemes aimed at reaching the remaining 10% of premises and stopping communities and others from identifying alternative ways of providing superfast broadband."
A DCMS spokesman said: "We disagree with the views expressed by the PAC, which are at odds with the findings of the National Audit Office."