Durham Police has been asked to “establish the facts concerning any potential breach of the law” surrounding Dominic Cummings’ visit to the county.
It emerged on Friday Boris Johnson’s top aide had travelled 260 miles to County Durham in March to self-isolate with his family while official guidelines warned against long-distance journeys.
Further reports over the weekend also suggested he took a second trip to the north-east of England in April, having already returned to work in London.
Mr Cummings denied the fresh allegations, which were reported by the Observer and the Sunday Mirror.
The adviser will make a statement and answer questions later on Monday.
Steve White, the acting police, crime and victims’ commissioner for Durham, has now formally written to the chief constable regarding information which he believes “deserves appropriate examination”.
In a statement, Mr White said: “I am confident that thus far, Durham police has responded proportionately and appropriately to the issues raised concerning Mr Cummings and his visit to the County at the end of March.
“It is clear however that there is a plethora of additional information circulating in the public domain which deserves appropriate examination.
“I have today written to the chief constable, asking her to establish the facts concerning any potential breach of the law or regulations in this matter at any juncture.
“It is vital that the force can show it has the interests of the people of County Durham and Darlington at its heart, so that the model of policing by consent, independent of government but answerable to the law, is maintained.
“It will be for the chief constable to determine the operational response to this request and I am confident that with the resources at its disposal, the force can show proportionality and fairness in what has become a major issue of public interest and trust.”
On Sunday, the Prime Minister said he believed Mr Cummings had acted “responsibly and legally and with integrity” amid a storm of controversy over the alleged lockdown breaches.
Follow STV News on WhatsApp
Scan the QR code on your mobile device for all the latest news from around the country