Congress should consider not funding any Fiscal 2017 Littoral Combat Ships while ensuring the Navy has an acquisition strategy for the replacement frigate program, a Government Accountability Office report on the programs' "fundamental weaknesses" recommended..

Plagued by years of cost overruns, design and survivability issues, then-Defense Secretary Chuck Hagel announced a plan in 2014 to limit LCS production to 32 ships instead of the 52 originally called for, the GAO report states.

Officials decided the gap would be filled with a multi-mission frigate. The LCS/frigate program was further winnowed to 40 vessels in December by Defense Secretary Ash Carter, who cited concerns about the sea service's balance between capability and quantity of platforms, the report states.

But while intended as a counter for the LCS issues, the GAO report released Thursday questions the frigate's future as well.

"GAO's analysis found the planned frigate will not provide much greater capability in some areas than LCS and that some cost assumptions may have overstated this options affordability," the report states. "As the Navy pivots from LCS to the frigate program, which is estimated to cost more than $8 billion for ship construction alone, its approach would require Congress to appropriate funding with key unknowns."

The Navy planned to procure one LCS from each of the two shipyards that manufacture them in 2017, at an average cost of $562 million, according to a May Congressional Research Service report.

This purchasing schedule means Congress would end up funding more LCS vessels "even though these ships have not demonstrated lethality and survivability capabilities," the GAO report states.

The sea service's plans involve both the Lockheed Martin and General Dynamics shipyards to complete construction of all LCS already under contract by 2021, but the GAO report cautions that both yards have experienced schedule delays of a year or more.

The modified LCS, or frigate, features additional built-in equipment and changes that make the ship harder for enemies to detect while improving the ship's ability to take battle damage, according to the Congressional research report.. They are heavier and slower than the baseline LCS as well.

The Navy does not plan to develop key frigate program documents or to reflect the program's cost, schedule and performance in the annual Selected Acquisition Reports submitted to Congress, GAO said.

"There are no current plans for official DOD milestone reviews of the frigate program, which is a major acquisition program based on its anticipated costs," the report states. "Without adequate oversight, federal funds may not be effectively spent."

Thursday's report is the GAO's latest in a long line of criticism against LCS, which was intended to be a highly mobile and modular surface vessel.

"Since 2005, we have raised many concerns about the Navy's acquisition of LCS, including its combat effectiveness and decreased expectations of its capability," the report notes. "Most recently, in December, 2015, we concluded that the lethality and survivability of LCS is still largely unproven, and that important questions remain about how LCS will operate and what capabilities it will provide the Navy."