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

Rayner is accused of potentially avoiding paying capital gains tax on her property – which she sold in 2015 – as well as potentially breaking electoral law. Rayner denies both allegations.

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.’ James Daly, deputy chairman of the Conservative party, had contacted Greater Manchester Police to report that Rayner’s neighbours believed her main residence was her husband’s property. The Labour line in response to the police statement is that the party ‘welcomes’ the investigation as an opportunity for them to put the matter to bed.

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 when asked about the story. Even before the investigation, the story had 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 interviews without it being brought 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. The defence is that she has received tax advice from an accountant which says that she has done nothing wrong. But Rayner has so far refused to publish this advice. Starmer says he has not personally seen the advice either, but 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 that it is wrong to draw parallels between her situation and Tory MPs in trouble over their tax affairs.

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. A case in point came today when Starmer refused to say whether Rayner would stay in post if the police find her guilty of an offence.

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 point out that Rayner previously asked Boris Johnson how he could stay on as prime minister when his Downing Street was being investigated by the police over partygate. Starmer’s issue is that even if he does believe Rayner’s position is untenable, he can’t actually sack her as deputy leader – it’s a position 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 until now.

Hear Katy Balls and Fraser Nelson discuss the latest on the Angela Rayner tax row on today’s Coffee House Shots: