Revamped policies that would guide FERC’s review of natural gas and liquefied natural gas infrastructure, as well as interim guidance for greenhouse gas (GHG) emissions, are likely to create more uncertainty and lengthier reviews, critics said.

In a split 3-2 vote, carried by the Democratic majority, the Federal Energy Regulatory Commission on Thursday issued policy statements to guide how future natural gas infrastructure is approved. The Commission also approved an interim GHG policy to ensure the “legal durability” of its decisions.

“There’s nothing remarkable, and certainly not radical, in taking environmental considerations into account while determining the public interest,” Commissioner Allison Clements said of approving the revisions.

The natural gas industry...