A Democratic Unionist Party (DUP) assembly member has joined MP colleague Carla Lockhart’s calls for Stormont’s First Minister Michelle O’Neill to be “removed from office”.

Diane Forsythe said “profound consequences” pledged over the Sinn Féin vice-president’s handling of the Drumcree parading dispute “must be honoured”.

Lockhart last week stepped down from the DUP’s officer board in response to party leader Gavin Robinson not removing their deputy first minister to force O’Neill from the joint office.

It follows unionist anger over the first minister’s involvement in protests on the Garvaghy Road, which blocked a contentious Orange Order parade from passing along the mainly nationalist street in Portadown, County Armagh.

O’Neill and several other senior Sinn Féin figures have been interviewed by police investigating the demonstrations, with unionists accusing the party of acting unlawfully.

The Sinn Féin deputy leader has defended her attendance at the demonstrations last month, saying she would “continue to stand with the Garvaghy Road residents”.

The political row has sparked differences of opinion over how to respond within the DUP, which shares power with Sinn Féin in Stormont’s devolved government.

Forsythe is an assembly member for the South Down constituency and part of the DUP’s party officer team.

In a post on Facebook on Monday night, Forsythe said she was “pleased” to show her support for Upper Bann MP Lockhart at a recent rally in Portadown.

She accused Sinn Féin of “arrogance” and described the feelings of anger in the unionist community over O’Neill’s actions as “immense”.

“There have been commitments made to deliver profound consequences and that it cannot be business as usual. These must be honoured,” 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 added that in the absence of such “meaningful action”, official engagements as first minister through the joint Executive Office should be stopped immediately as a “bare minimum”.

Last week Robinson said he was “sorry” to see Lockhart quit the DUP’s officer board but added that she remained “a key part of our team”.

Speaking on the BBC’s The View programme, the DUP leader said the party had reached a democratic decision on how to deal with the Drumcree fallout.

He questioned whether it was necessary to “punish everyone in Northern Ireland when actually we should be punishing those who broke the law”.

“We have considered all options and we keep all options on the table,” he added.