That Rishi Sunak is being investigated over his wife’s share dealings is a major blow for a prime minister who vowed to prioritise ethics – but it may not surprising given his entire government appears to be in breach of the ministerial code.

The investigation, confirmed today by the parliamentary commissioner for standards, is believed to relate to KoruKids, a firm in which Sunak’s wife, Akshata Murty, is a major shareholder and which benefitted from payments introduced in last month’s budget.

The probe is being triggered through Parliament’s “new code”, which Sunak brought in four months ago in a bid to draw a line under the sleaze of the Boris Johnson years.

In his first speech as prime minister in October, Sunak promised to bring back “integrity, professionalism and accountability at every level”. And in his leadership election against Liz Truss, he vowed that his government would prioritise “competency” and “decency”.

Yet appearing before the Liaison Committee of MPs last month, Sunak was specifically asked why the budget's incentive payments favoured private firms – but he did not mention that his wife was a major shareholder in one of the firms benefiting.

Under Parliament’s rules, MPs are normally expected to declare any relevant interests they have when answering questions.

It is not the first time Murty’s extensive shareholdings have raised questions for the prime minister. In February, it emerged that she had shares in a company that benefited from £300,000 in emergency Covid loans when Sunak was chancellor.

Sunak also previously received scrutiny over his wife’s shares in her billionaire father’s software firm – fielding questions on everything from his wife’s net worth – estimated to be hundreds of millions of pounds – to whether she benefitted from trading in Russia, something they deny.

Has Sunak breached the rules?

The prime minister’s position is that he has followed the rules at all times and declared his wife’s shareholding by disclosing it to the government’s ethics adviser.

However, Sunak’s declaration has never been made public. The last list of ministers’ interests, published in May 2022, makes no mention of his wife’s shareholding in KoruKids. Nor is there any mention in the MPs’ register of interests.

This is because of the way transparency rules work for ministers.

There are two sets of disclosures that every minister must make – one as a minister, and one as an MP. Declaring something on one list allows a minister to not omit it from the other.

But over the past few years, the government has repeatedly failed to publish the twice-yearly list of ministers’ interests that it is required by law to publish. As openDemocracy reported last December, Sunak’s entire government appears to be in an ongoing breach of its own ministerial code – something a government spokesperson denied at the time.

Even when the government does publish a list of ministers’ interests, it does not always include all the interests that ministers have declared in private. Occasional leaks suggest there is a “secret register” that the public never sees.

These loopholes have allowed Sunak to say that he has declared his wife’s interests, while none of the declarations have so far been made public by the government.

A spokesperson for the prime minister said: “We are happy to assist the commissioner to clarify how this has been transparently declared as a ministerial interest.”