UK police announced on Friday that they have launched an investigation into the deputy leader of the opposition Labour party over claims she may have broken electoral law.

Ruling Conservative MPs have accused Angela Rayner of giving false information about her main residence to avoid paying full tax on the sale of her house in 2015.

Rayner strenuously denies wrongdoing and has accused Conservatives of a "manufactured" smear as they try to narrow polls before this year's general election.

"We have seen the Tory Party use this playbook before -- reporting political opponents to the police during election campaigns to distract from their record," she said in a statement responding to the news.

"If I committed a criminal offence, I would of course do the right thing and step down. The British public deserves politicians who know the rules apply to them."

Rayner added the questions raised "relate to a time before I was an MP" and that she had taken expert tax and legal advice regarding her family's circumstances then.

"I look forward to setting out the facts with the relevant authorities at the earliest opportunity," she said.

Greater Manchester police had initially said it would not investigate the Labour deputy, but changed its stance following a complaint from Conservative deputy chairman James Daly.

"We're investigating whether any offences have been committed," a spokesperson said.

"This follows a reassessment of the information provided to us by Mr Daly."

Rayner, 44, insists that she followed the rules when she sold for a profit her former council house, which she had declared as her principal residence on the electoral register.

Daly has reportedly told police that neighbours believed Rayner was living with her then-husband at his home, possibly making her liable for capital gains tax.

Labour leader Keir Starmer has backed Rayner and a party spokesperson said: "Angela welcomes the chance to set out the facts with the police."

Labour, in opposition since 2010, are soaring ahead of the Tories in opinion polls.

Prime Minister Rishi Sunak has said the election will be in the second half of the year, but is yet to name a date.