Britain's August oil output slumped to its lowest level for more than 16 years, preliminary government figures have shown.
Seasonal field maintenance and rapid decline rates combined to reduce total oil output - including small onshore operations and natural gas liquids - to 6,063,000 tonnes.
The last time output was lower was in June 1989 as operators improved safety on rigs following the 1988 Piper Alpha disaster, the data from the UK's Department of Trade and Industry showed.
"We saw a significant drop in production," said Thorsten Fischer, an energy economics analyst at the Royal Bank of Scotland.
"That is partly because of the trend of declining output as North Sea fields are maturing, but it's mostly attributable to maintenance."
Ouptut of oil alone stood at 1.35 million barrels per day, down 13.1 per cent from 1.56 million bpd in July.
UK output has declined at a faster rate than expected since it peaked in 1999.
The North Sea output slide has contributed to deteriorating expectations for global ouptut from producers outside the OPEC cartel in 2005. Non-OPEC output growth in 2005 was expected to come in at 170,000 barrels per day, according to the Paris-based International Energy Agency.
That would be the lowest growth rate in six years as non-OPEC countries struggle to bring enough new oil on stream to compensate for decline from mature regions such as the North Sea.
The North Sea's largest producer, Norway, also saw one of its poorest months of production for more than a decade in June.
UK August output was also hit by a fire at BP's Schiehallion field, which knocked out about 120,000 barrels per day for most of August.
Total ouptut in September should rebound as Schiehallion had restarted and as the seasonal maintenance season ends, Mr Fischer said.
Record oil prices should have acted as a further incentive to restart output from North Sea rigs as quickly as possible, he said.
In June 1989, total oil production was 5,600,000 tonnes. An explosion on the Piper Alpha platform in July 1988 killed 167 people and forced operators to make changes to improve safety.