What does the parliamentary standards watchdog investigation mean for Boris Johnson?

How the prime minister paid for a £15,000 luxury holiday with his fiance is under investigation

(PA)

Boris Johnson is under investigation by parliament's standards watchdog amid questions about how he paid for a £15,000 luxury break to the island of Mustique.

Here's everything you need to know about the investigation and what it means for the prime minister.

Who is investigating the prime minister?

The watchdog investigating the prime minister is called the Parliamentary Commissioner for Standards - whose name is Kathryn Stone.

An independent officer of the House of Commons, the Commissioner is responsible for investigating whether MPs have breached the MPs' code of conduct.

Separately she also has oversight of investigations into complaints against MPs about harassment bullying, and abuse, and keep tabs on MPs' Register of Members' Financial Interests – a record of any potential conflicts of interests.

The nature of the allegations means the prime minister is being investigated as an MP, rather than in this role as the head of the government.

What is the allegation against Boris Johnson?

Boris Johnson went on a luxury £15,000 trip to Mustique with his fiancé Carrie Symonds over a year ago. He stated on his register of interests that the trip was paid for as a “benefit in kind” from David Ross, co-founder of the company Carphone Warehouse.

But Mr Ross subsequently told the Daily Mail newspaper that he had not paid for Mr Johnson's trip and did not own the villa - and had only helped put him in touch with companies providing the accommodation.

17 months later the PM has not said who paid for the trip, as rules say he should.

Which rule is he alleged to have broken?

The Commissioner says the prime minister may have broken the rule that “members shall fulfil conscientiously the requirements of the house in respect of the registration of interests in the register of members’ financial interests.

"They shall always be open and frank in drawing attention to any relevant interest in any proceeding of the house or its committees, and in any communications with ministers, members, public officials or public office holders.”

What sanctions could be imposed by the commissioner?

This would depend on how serious the offence is. If found in breach of the rules, the prime minister could merely be forced to apologise.

But if the commissioner determines the breach is serious enough, it could be a referred to a committee that would have the power to recommend further sanctions.

These range from temporary suspension from the Commons to expulsion – though this is incredibly rare.

What does the prime minister say about it?

The prime minister’s spokesperson on Monday perhaps deliberately glossed over the details of the case outlined in this article, telling reporters: “The prime minister transparently declared the benefit in kind in the Commons register of interests ... Clearly the rules are set out and it’s important that everyone abides by them, as the prime minister has done throughout.”