The Brent pipeline network in the North Sea, which services up to 27 oil fields, has been closed temporarily.
The shutdown followed the detection of a leak on the Cormorant Alpha platform off Shetland, which handles around 90,000 barrels per day of crude oil.
Workers have been airlifted off the rig as the leak is investigated, the platform's operator Abu Dhabi National Energy Company (TAQA) said.
Eight other platforms in the area have been closed as a result of the incident.
Industry body Oil & Gas UK said the affected pipelines transport a significant amount of the UK's oil.
"We estimate that oil usually produced from the fields that are currently shut down across the Brent Pipeline System accounts for about ten per cent of UK oil production," economics director Mike Tholen said.
"We have offered support to TAQA Bratani during the incident and await more information on how long the shutdown is likely to last."
A company statement said: "TAQA can confirm that an indication of hydrocarbons was detected in one of the legs of the Cormorant Alpha platform in the northern UK North Sea.
"Since the discovery, hydrocarbon levels have been continually monitored.
"The platform and all pipeline infrastructure have been shut down as a precaution."
It stressed that none of the hydrocarbons found on the legs of the rig, which is 94 miles from Lerwick, had been released into the environment.
Energy analyst Neil Atkinson from Datamonior said the closure was unlikely to affect oil prices if it reopened soon.
"The only real significance of this event is how long it lasts for," he told Sky News.
"If it's only closed for a couple of days it is unlikely to affect the market - the UK has plenty of stock elsewhere.
"It becomes as issue if the pipeline network remains shutdown for a significant amount of time - ten days for example - and refining operations are curtailed because of a lack of crude oil."