The row over Angela Rayner’s tax affairs is becoming more serious. This morning, Greater Manchester Police have launched an investigation into the Labour deputy leader over whether she broke electoral law by failing to properly disclose her main resident in official documents. This relates to two properties in Stockport – one owned by her (on Vicarage Road) and one by her then husband Mark Rayner (on Lowndes Lane) – and whether Rayner’s primary residence was her former husband’s despite claiming otherwise.

Rayner is accused of potentially avoiding paying capital gains tax on the property – which she sold in 2015 – and potentially breaking electoral law by failing to properly disclose her main residence in official documents. Rayner denies both allegations. Announcing the news of the investigation, a police spokesperson said: ‘We’re investigating whether any offences have been committed. This follows a reassessment of the information provided to us by Mr Daly.’ It comes after James Daly, deputy chairman of the Conservative party, got in touch with Greater Manchester Police to report neighbours claiming that Rayner’s main residency was her husband’s property rather than the property she owned, as she has previously claimed.

Today’s development will only up the pressure on Rayner and her colleagues

So, where does this leave Rayner? Of course, the police investigation is not the same as the police finding her guilty of an offence. But it is nevertheless a significant development. So far, Rayner’s team have been able to say there is no live police investigation. Even without one, the story has become increasingly uncomfortable for Labour. Keir Starmer has been repeatedly asked about it out on the campaign trail as he tries to focus the news agenda on his local election messaging. Other shadow cabinet members can’t do media without it coming up. It’s also starting to come up on the doorstep with voters.

Starmer has said he backs Rayner and is satisfied with her defence. That defence is that she has received tax advice from an accountant that she has done nothing wrong. However, Rayner has so far refused to publish the advice. Starmer says he has not personally seen the advice despite being a lawyer, saying his team have instead. David Lammy has suggested Rayner is being attacked because she is a ‘northern woman’. Those close to Rayner believe she is being unfairly targeted and parallels with Tory MPs in trouble over tax are wrong.

However, today’s development will only up the pressure on Rayner and her colleagues – some of whom are already getting fed up with having to spend airtime defending her on the story. The Tories have been pushing for the police investigation (as well as an HMRC investigation over the capital gains allegation) because they believe even if she hangs on it will stink of hypocrisy. Tory MPs are pointing to how Rayner previously asked how Boris Johnson could stay on as prime minister when his Downing Street was being investigated by the police over partygate. Starmer’s issue is even if he did believe Rayner’s position was untenable he can’t actually sack her as deputy leader – it’s a position for which she was picked by the membership. It means Starmer and Rayner could soon need to find a stronger and more transparent line of defence than what has been offered up til now.