A second Democratic Unionist Party (DUP) politician has publicly called for the removal of Michelle O'Neill as Northern Ireland's First Minister over her participation in a protest on the Garvaghy Road in Portadown last month.

South Down MLA Diane Forsythe has joined Upper Bann MP Carla Lockhart in urging the DUP to withdraw deputy First Minister Emma Little-Pengelly from the Stormont Executive, a move that would automatically force O'Neill from her post because of the joint nature of the power-sharing structures.

Such a step would effectively collapse the devolved administration, although other individual departmental ministers would remain in post and the Assembly could continue to sit for a further six months.

The Garvaghy Road protest was held on the day an Orange Order parade was due to proceed along the road for the first time in almost 30 years. The Parades Commission had allowed the parade, but it was ultimately banned by Northern Ireland Secretary Chris Bryant because of significant numbers of protesters. Police have said invitations to attend interviews were sent to individuals "reasonably suspected of committing offences". Under parading laws, protests must be notified to and approved by the Parades Commission.

O'Neill and several other prominent Sinn Féin figures, including party leader Mary Lou McDonald, have attended police interviews about their participation. Arriving at Musgrave Street PSNI station in Belfast, O'Neill said she would not resign as First Minister if prosecuted, adding: "It was always the right thing to do to stand on the Garvaghy Road."

DUP leader Gavin Robinson has defended his party's decision not to withdraw Little-Pengelly, saying the party had reached an "agreed position" and that collapsing the Executive would damage unionism. Lockhart resigned as a DUP party officer last week over this difference of opinion.

In a social media post, Forsythe wrote: "The overwhelming majority of Unionist people believe Michelle O'Neill should not be First Minister of Northern Ireland. The anger felt towards her across Northern Ireland is immense and I strongly share in that anger."

She added: "It is my view that Michelle O'Neill should be removed from office. The Assembly and other Ministerial Offices would continue until the next election."

Forsythe said that in the absence of such meaningful action, Little-Pengelly should stop participating in joint engagements with the First Minister as a bare minimum.

Sinn Féin Infrastructure Minister Liz Kimmins has said O'Neill is "going nowhere", stating: "The people decided who the First Minister of the North is and that's the way that will remain." Kimmins confirmed she has received a police invitation for interview in the investigation and said she would cooperate.