A Sussex accountant is warning businesses to start planning for the euro before they get left behind.

John Guest, partner at the Brighton office of accountancy firm Hacker Young, said many people were unaware of how the new currency would impact on them.

On January 1, the 12 countries participating in the first wave of the single European currency will adopt the euro.

Mr Guest said: "We may not yet be in the single currency, but we are certain to be affected by it.

"Many businesses in the UK trade with other European countries. These countries will have to be paid in euros and UK businesses should, by now, be fully prepared.

"However, because many businesses have put the issue on the back burner they are not fully prepared for the impact."

For a short period until the end of February, both old and new currencies can be used in a eurozone country, to use up any notes and coins. After that, the euro will be the only currency accepted.

Mr Guest said: "Holidaymakers need to know many currencies, including pesetas, francs and Deutschmarks, will become defunct with a few weeks.

Most major banks now issue only euro and sterling travellers cheques to people travelling to any of the eurozone countries.

People should spend any national currency abroad or make sure they exchange unused notes as soon as they return."

After withdrawal, unsued notes will be exchangeable at banks, incurring extra charges and delays.