A Momentum Midstream LLC affiliate has joined two natural gas pipeline operators in accusing Energy Transfer LP of upending industry practices for pipeline crossings in Louisiana, which they said threatens to stall development of the Haynesville Shale and growth of LNG exports.

New Generation Gas Gathering (NG3) LLC, a Momentum affiliate, said its $1.6 billion pipeline and carbon capture project has been put on hold after Energy Transfer sued to block the project from crossing the midstream giant’s Gulf Run Pipeline.

“Energy Transfer is blatantly and openly engaged in anticompetitive conduct and unfair trade practices in violation of Louisiana law” by using Gulf Run in an attempt “to secure a stranglehold on the movement of natural gas out of northwestern Louisiana,”...