Britain came within an ace of becoming a net oil importer for the first time in 13 years in May, helping the country's trade deficit widen unexpectedly to £3.4 billion.
National Statistics said that the surplus on trade in oil was £137 million in May compared with £184 million the month before and nearly £400 million in March.
By volume, imports have already exceeded exports, with inflows of 4.91 million tonnes of oil in May exceeding inflows of 4.80 million tonnes.
Britain has not since August 1991 announced, by value, higher imports of oil than exports from its North Sea fields. While deficits were initially reported for September and April the figures were later revised to show surpluses.
Analysis of underlying data, however, has revealed that Britain may soon take on permanently to the status of oil importer, with North Sea production, which peaked at 2.9 million barrels a day in 1999, set to fall to near half that level by 2007.
The country's position in oil trading has become particularly important in recent months when Middle Eastern tensions, and shortfalls in US stockpiles, have sent oil prices to their highest levels since the 1980s.
The data was announced as National Statistics revealed that the UK trade deficit widened in May despite a 4 per cent surge in goods exports to European Union nations. Exports to countries outside Europe fell by 3 per cent.
National Statistics said: "The latest estimate of the rend suggest that the goods deficit is widening. The trends in the value of trade show exports falling and imports flat."
The data was viewed as offering little short-term threat to the UK economy.
However, the Centre for Economics and Business Research warned of "a nasty surprise may well come sometime in the next few months".
The CEBR said: "The UK's trade in oil is steadily moving from comfortable surplus to deficit, and economic slowdowns in China and the US may hamper UK export growth to these key markets.
"Meanwhile the UK's appetite for imports remains voracious."