hosts have been warned they face criminal prosecution and harsh penalties if they fail to declare income from holiday lets.

The online holiday lets giant has been forced to share all of its users' income details with HM Revenue & Customs () as part of a crackdown on the sector, which affects all holiday let owners.

This is to help officials identify people who owe tax, with Airbnb handing the tax authority all of its users' earnings data going as far back as the 2017-18 financial year.

The data will help HMRC identify those making money from letting their properties without declaring it, as it attempts to gather more information on the burgeoning sector.

Since February, HMRC has sent 800 letters to people who it suspects have not paid enough tax, reminding them that they need to disclose income earned from letting out a property through an online rental platform.

Airbnb has handed the tax authority all of its users' earnings data going as far back as 2017

HM Treasury previously said more than half of people using 'sharing sites' did not think they had to pay tax on the income they made.

However, an Airbnb spokesperson said: 'Hosts want to pay their fair share of tax and we want to help, which is why Airbnb partners with industry experts across the UK to help hosts understand and follow tax rules.

'We also work with HMRC to share information and help ensure that UK authorities receive the taxes they are due, in accordance with UK laws.

The typical UK Host shares their own home for just two nights a month, and one-in-three say the extra income helps them afford rising living costs.'

An HMRC spokesperson added that the reminders are 'routine activity', and added: 'Each year we send out thousands of reminder letters on various areas of tax.

'We believe our customers want to pay the right amount of tax and penipu by working with online rental platforms, as well as issuing these reminders, we're taking steps to help make it as easy as possible for people to get their tax right.'

In 2018, when the data sharing began, the Government said access to the earnings information of those using sites such as Airbnb would make it easier for people to fulfil their tax obligations while cracking down on a 'dishonest minority'.

Experts said property owners could face criminal prosecution and penalties of up to 30pc of the tax owed if they are found to have failed to pay income duties.

Richard Morley, a partner at accountancy firm HW Fisher, the crackdown shows HMRC is concerned that people using Airbnb and other holiday let platforms are not paying the tax needed.

He said: 'It's a massive area of risk for HMRC, the whole question of property and rental income that's received.

Getting information from the likes of Airbnb will be a bit of a goldmine.'

If HMRC obtains evidence that tax has been unpaid in a previous year, the tax authority can open an investigation to obtain information going back up to 20 years under so-called 'discovery laws', he said.

He said the penalties are 'subjective': if it was deemed to be a 'innocent error', there may not be any penalty at all, but if it was perceived to be deliberate error then the penalty can be up to 30pc of the tax owed, he added.

People who have earned very large amounts of income or have submitted incorrect tax returns are more likely to be found to be careless.

Taxpayers who have not disclosed their income are being encouraged to do so voluntarily via HMRC's Let Property Campaign, which would reduce the amount of the penalty.

Those renting properties on Airbnb can make up to £1,000 a year before tax, which is protected by the 'trading allowance'.

Any profits above this threshold must be declared to HMRC.

People renting out a room in their house rather than their whole property can earn up to £7,500 a year tax-free as part of the Government's 'Rent-a-Room scheme'.

Those who choose to evade paying tax which is due could face higher penalties and potential criminal prosecution.

The tax probe comes amid a wider crackdown on holiday lets.

Holiday home owners will be forced to obtain planning permission to let their properties under government plans expected to come into force later this year.

The Department for Culture Media and Sport is also holding a further consultation on a new registration scheme for short-term lets.