Rupert Grint has lost a legal bid to claim a £1 million tax refund.

The Harry Potter film star had launched an appeal after he was barred from using a technical change to reduce the amount of his earnings subject to an increased top tax rate.

A specialist judge today sided with HM Revenue and Customs in the dispute after it blocked him from making the change.

Grint, who is thought to have made around £24 million from playing Ron Weasley in the wizarding film series, would have saved around £1 million had his challenge succeeded.

The tax tribunal judge stressed it was not part of HMRC's case that Grint was involved in tax avoidance.

The 27-year-old actor had followed advice from tax advisers Clay & Associates to change his accounting date so that a total of 20 months of income would fall to be taxed in 2009-2010.

It would have meant that an extra eight months worth of income would be taxed at 40% instead of the increased 50% top rate which was brought in for the following 2010-2011 tax year.

The judge ruled that Grint had failed to properly document that such a change had been made to that effect in his accounting documents.

During the hearing of his challenge, Grint, who first appeared in the Potter films at the age of 12, had admitted that his knowledge of his financial affairs was "quite limited", and that he left his tax returns to his father, Nigel, and his accountant Dan Clay.

The judge said in her ruling that he had made it clear "that he placed his faith in his father and accountants to deal with his financial affairs".