Hundreds of companies online, many of whose websites resemble the official website of the American government, are inviting people from all over the world to sign up to their visa application service.

For a fee of anything between $30 and $100, these companies promise to process a person's visa application and make sure it is correctly filled in before submitting it. Some offer free flights to the US on the offchance that the customer wins a green card.

"There are a lot of fraudulent websites out there that Irish people should be aware of, " said Danny Toma, consul at the American embassy in Dublin.

"Many of these take your money and you never hear from them again. There are others that, while not necessarily fraudulent, are still offering a questionable service and charging for it.

"Applying for a visa online is a simple process that takes five minutes and requires no intermediary, " said Toma, adding that "the American government charges no fee whatsoever for entering the visa lottery".

Every year, the American Diversity Lottery (DV) Programme grants 50,000 visas to people all around the world. This allows the visa winners and their immediate families to live, work and acquire an education in the United States. Last year, 145 Irish people won an American visa.

According to Toma, people should carefully check any websites that are now accepting applications for the next green card lottery, DV 2008, which does not open until the autumn.

"The rules for applications have not yet been released, and while they are likely to be roughly the same as last year, slight changes can often be made, " he said.

"Websites which are encouraging people to apply now, even if they are acting in good faith, are making a whole lot of assumptions and should be avoided."