Instead Britain will be represented by Sir Stephen Wall, its ambassador to the EU, when finance ministers gather in Brussels.
The event will include the announcement of the exchange rates of the 11 currencies taking part in the euro, which begins life tomorrow. Signing of official regulations will be followed by a champagne reception and the release of 3,000 balloons.
With Britain not taking part in the first wave, the event has been a presentational minefield for the Government. The Chancellor could not expect to enjoy a position centre-stage, but staying away could be interpreted as a lack of commitment to Europe.
In the event, Mr Brown will not be the only prominent absentee. Oskar Lafontaine, the German Finance Minister, is on holiday and his place will be taken by the former businessmen, Werner Muller, an economics minister.
The Treasury believes that the finance minister of at least one of the three other countries not taking part in the launch will also stay away. All 15 EU finance ministers were invited.
British officials in Brussels also pointed out that Mr Brown suffered a family bereavement before Christmas, making any prospect of his attendance more difficult.
A Treasury spokeswoman said: "This is just a presentational meeting and Sir Stephen Wall will represent the UK. The meeting is not likely to last more than an hour and there will be no decisions affecting Britain or other countries not taking part."
Nevertheless, today's celebrations have been given considerable billing in Brussels, where the arrival of the single currency is seen as a landmark, and Mr Brown's absence will be a disappointment to enthusiasts for British entry.
The European Commission has spent pounds 35,000 to publicise the event when exchange rates will be locked and the power to set interest rates in the 11 countries taking part handed over to the European Central Bank. Notes and coins will not be introduced until 2002.
Countdown to the euro,
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