The commission will ignore a last-minute compromise by Treasury ministers to end a three-year dispute over the impounding of cheaper, duty-paid cigarettes and wine bought at French and Belgian hypermarkets - and even of shoppers' cars.
The row over "disproportionate penalties" has seen the outgoing British commissioners, Neil Kinnock and Chris Patten, side with the government in lobbying their colleagues to withhold support for the legal action sought by Frits Bolkestein, the internal market commissioner.
But in what is being seen in Whitehall as "Bolkestein's last stand" before he leaves next week after bruising battles with the chancellor, Gordon Brown, over this and other issues, the commission will take the UK to the European court of justice in Luxembourg.
Last week it enraged Germany by taking it to court over the "VW law" protecting Volkswagen from hostile takeover.
The row hinges on the treatment of Britons who exceed "indicative" guidelines by bringing home more than the 800 cigarettes, 90 litres of wine and 110 litres of beer and "selling" them on to family and friends on a not-for-profit basis. Customs believes the imported goods, often bought at half UK prices, are sold on the black market.
The economic secretary, John Healey, last week wrote to Mr Bolkestein saying that customs officials would submit compromise proposals "within the next two weeks" - too late for the outgoing commissioner to act.
British sources said the government, which has a long-running campaign against smuggling and its multi-billion drain on Treasury coffers, had given a verbal assurance that Customs would no longer seize the cars of first-time offenders and would henceforth allow people to keep the goods on payment of duty owed and a proportion of the fine.
A commission official said it was "purely a tactical manoeuvre by the Brits, who are playing for time".
