US Senator John McCain has opposed the US Navy's decision to buy ten coastal warships each from Lockheed and Austal and has suggested picking just one design.
McCain said US Congress lacked the basic information required to make an informed decision about the plan.
"Without the basic information needed to make an informed decision on the Navy's proposal and without the benefit of thoughtful and transparent oversight, I cannot support the proposal at this time," he said.
US House lawmakers have introduced a measure to approve the plan, although the proposal still needs Senate approval, according to Reuters.
The new Government Accountability Office report said the programme faced design and construction risks, and that the programme's costs could rise if the navy adopted more design changes to the new ships.
"As such, decision makers do not have a complete picture of the various options available to them," the report said.
The US Navy also had not analysed the savings associated with the early retirement of the losing ship design if it failed to win congressional approval to buy both.