A sudden change in the tactics used by perpetrators of huge and persistent VAT frauds has skewed the official trade numbers for June by hundreds of millions of pounds and set alarm bells ringing in Whitehall.
The so-called "Missing Trader Intra- Community Fraud" was first detected more than two years ago.
Shadowy organisations and individuals were found to be importing container loads of mobile phones and computer parts, selling them at prices including a 17.5 per cent VAT charge, then vanishing without passing the tax on to the Customs & Excise.
It is believed the phones were later re-exported then re-imported for a second, third or fourth fraud. The entire operation appeared to take place between European Union countries.
In June, though, Britain's exports of goods to non-EU countries jumped inexplicably by £1.1 billion to £8.45 billion in figures already adjusted by National Statistics to take account of the known pattern of fraud.
Exports to Dubai alone jumped by £ 329 million between May and June to £ 529 million, up from £131 million in June last year. Russia took British goods worth £141 million, but none at all a year earlier.
"We have recognised this in the last two weeks," said a Government statistician.
"What is happening here? How is it happening?
"The scale of the change has raised alarm bells."
The Customs, now merged with the Inland Revenue, said: "As often happens when tackling organised crime, our success has prompted changes in the fraud including, in this case, changes to the underlying pattern of trading.
"We are analysing recent trade data to determine if this impacts on balance of trade figures."
Statistical provisions to account for the known form of "missing trader" frauds in the national accounts peaked at £11 billion a couple of years ago and led to successful prosecutions, an NS spokesman said.
NS and HM Revenue and Customs officials are now considering whether adjustments to the trade figures may be needed to take account of frauds involving countries outside the EU.
The official numbers for June show that Britain's overall UK trade deficit in goods narrowed to £4.3 billion in June from £5.0 billion in May.
The surplus on trade in services rose to £1.8 billion from £1.49 billion in May, trimming the overall trade gap for the month to £2.48 billion from£3.49 billion.
Over the second quarter of this year, the shortfall in Britain's total trade with the rest of the world narrowed to £ 9 . 66 billion from £10.32 billion in the three months to March.
Exports of goods rose by 7.7 per cent to £52.185 billion, while imports were 4.1 per cent higher at £66.57 billion.
Britain remain selfsufficient in oil in June, with a surplus of £204 million from trade in oil.
Over the second quarter of this year, oil yielded a £481 million, £18 million less than in the first three months, but £90 million more than in April/June last year - boosted by the surge in the price of oil in the meantime.