Natural Resources Wales (NRW) has issued an enforcement notice to suspend the use of two fuel pipelines on the Valero Refinery jetty in Milford Haven.
The notice was issued after pollution incidents affected water, land and wildlife along the coast in December and the first week of January.
It means that the two pipelines believed to be behind the pollution are shut down until NRW is satisfied that they can be used without threatening the environment.
A multi-agency response including clean-up work continues on the affected section of coastline following the most recent oil spill.
Valero and its contractors are working on cleaning the coastline at Milford Haven while NRW, Pembrokeshire County Council and Pembrokeshire Coast National Park Authority monitor and advise.
Since the initial report of pollution, efforts have focused on minimising the impact of the oil on the area and its wide range of wildlife.
The affected sites have continued to be cleaned and the oil from the leak has been contained.
Andrea Winterton, Operations Manager from Natural Resources Wales said:
“Protecting Wales’ waters is a huge part of our job and we have acted to make sure that the estuary and its wildlife is protected.
“A quick, multi-agency response to this incident has helped reduce the impact of the oil spill in the area.
“Beach surveys continue and as a precautionary measure booms remain in place to protect the salt marshes around Sandy Haven and the Gann Estuary.
“Valero has already implemented additional measures to minimise any further impact and is co-operating as our investigations continue.
“We ask people to remain vigilant, avoid any oil if they discover it, particularly if they have dogs, and contact the NRW incident hotline on 0300 065 3000 if they become aware of any pollution.”