Upper Bann MP Carla Lockhart said Monday she had resigned from the Democratic Unionist Party and would sit in the House of Commons as an independent unionist, after a dispute with party leaders over their response to the Drumcree parading standoff in Portadown, County Armagh^1,2.

Lockhart had called on the DUP to withdraw its deputy first minister from office, a step that would also remove Sinn Féin First Minister Michelle O'Neill from the joint post^1,2. RTÉ identified that DUP figure as Emma Little-Pengelly².

The dispute followed unionist anger over Sinn Féin figures taking part in protests on Garvaghy Road that blocked an Orange Order parade along a mainly nationalist street^1,2. BBC and RTÉ reported that O'Neill and other senior Sinn Féin figures have been interviewed or are being investigated by police over the demonstrations^1,2. O'Neill has said her involvement was the right thing to do, according to BBC¹.

Last week the DUP, which shares power with Sinn Féin at Stormont, stopped short of collapsing the executive and instead said it would block official engagements involving O'Neill^1,2. RTÉ said Little-Pengelly would also withhold permission for O'Neill to carry out some solo first minister engagements².

In a Facebook statement quoted by BBC, Lockhart said her first responsibility remained to Upper Bann and that she was leaving on a "point of principle"¹. RTÉ published excerpts from a letter to DUP leader Gavin Robinson in which she said the party's response had "fallen far short of the profound consequences promised" and also cited the Irish Sea border².

The DUP said it regretted her resignation, thanked her for her work, and said further divisions within unionism would benefit Sinn Féin¹. It said it shared unionist anger at O'Neill's actions but disagreed on the course that would secure accountability¹.

BBC's Northern Ireland political editor said Lockhart had been on a collision course with the leadership for weeks and that Robinson had the support of the party's officer and assembly teams¹. BBC said the DUP would be left with four MPs, down from a previous high of 10, with an assembly election about seven months away¹.