Prime Minister Rishi Sunak has been reported to police in Scotland after making a joke about former First Minister Nicola Sturgeon in his speech to the Tory party conference.

Mr Sunak sought to humour delegates with a reference to her arrest and questioning in June as part of Police Scotland’s Operation Branchform investigation into her party’s finances. The former SNP leader was released without charge.

The Tory leader told the Manchester audience that the union between Scotland and the rest of the UK was “the strongest it has been in a quarter of a century” and “the forces of separatism are in retreat”.

He went on to make a joke about Ms Sturgeon’s hopes of “going down” in history as the woman who broke up the United Kingdom, then suggested she might go to jail.

Chris McEleny, the general secretary of the rival pro-independence Alba Party, has made contempt of court allegations against the Prime Minister as his comments come amid a live police investigation.

Mr McEleny said: “It is too important a matter to allow interference from the Prime Minister in this act of contempt when many people await the facts of Police Scotland’s investigation.”

Police Scotland’s investigation into SNP finances concerns allegations that £666,953 raised since 2017 specifically for a second independence referendum campaign was in part improperly spent.

Former SNP chief executive Peter Murrell, who is married to Ms Sturgeon, and ex-SNP Treasurer Colin Beattie were also arrested and later released.

In his conference speech, Mr Sunak confirmed that the Birmingham to Manchester leg of the HS2 rail line would not go ahead, though it would reach Euston as planned. The £36bn allocated to the northern phase would be invested in transport projects across the country. This includes resurfacing roads.

His decision on HS2 has caused deep divisions. Former PM David Cameron said it was the wrong decision, meaning a “once-in-a-generation opportunity was lost”.

Mr Sunak was introduced to the stage by his wife – Akshata Murty – who described her husband as her “best friend”.

She said: “We are one team and I could not imagine being anywhere else but here today with all of you to show my support to him and to the party.”

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