Ulster Unionist MP Danny Kinahan has apologised for posting a photograph on Twitter which showed him standing in front of a Co Antrim bonfire with an Irish tricolour placed on top of it.
The South Antrim representative posed for the photograph while holding a cheque for charity.
Mr Kinahan said it had been an error of judgment.
He said: "What I wanted to get across was here was a family, rural bonfire scene and they'd raised £600 for meningitis.
"They were having fun and this is Protestant culture - let's recognise each other's cultures and get on with it."
Mr Kinahan attended a Dublin ceremony last weekend recognising the Irish dead at the Somme.
Alliance leader David Ford tweeted: "On Saturday you showed respect for the Irish flag, as the state respected those who died at the Somme.
- on Saturday you showed respect for the Irish flag, as the state respected those who died at the Somme. Do you approve of this hate?— David Ford ex-MLA (@DavidFordxMLA) July 11, 2016
"Do you approve of this hate?"
A number of other Irish flags and Sinn Féin election posters were burned during other Eleventh Night bonfires.