The fines handed out by HM Revenue and Customs to those people who file their tax returns late are unfair and indiscriminate, according the law firm McGrigors.

One-and-a-half million people were fined by the taxman this year for filing a late tax return, while the penalities have gone up by 56 per cent in five years.

The maximum penalty now stands at £1,500 depending on how much tax was owed, compared to a maximum of £100 just five years ago. The smallest fine is now £100 for returns filed one day late, plus £10 for each additional day. For those returns six months late, the taxpayer is charged £300 or five per cent of tax owed -- whichever is highest.

Jason Collins, from McGrigors, said that those who have a "reasonable excuse" for missing the tax return deadline should appeal any fine.

He adds: "The majority of taxpayers do not bother to appeal because they assume that HMRC issues fines strictly in accordance with the law." However, he added that with HMRC issuing stiffer penalties this year, more people are likely to challenge a penalty fine.

A spokesman for HMRC said that the increased fines were used to encourage people to file their returns on time, and not as a way of making money.

"We want tax returns back not penalties, so nobody will receive a penalty where they file a tax return by the deadline or have a reasonable excuse for failing to do so," he said.

The next tax deadline is 31 October. Any paper returns sent after this date will incur a fine.