DUP assembly member Jim Wells has said he is "appalled" that an advice centre used by Sinn Féin MP Chris Hazzard is named after two prominent IRA men.
Sinn Féin leader Mary Lou McDonald was recently pictured at the reopening of the 'McNulty - Magorrian Advice Centre' in Castlewellan.
It is used by Mr Hazzard as his official constituency office.
Peter McNulty (47) was killed in January 1972 when a bomb he was placing outside the town's RUC station exploded prematurely.
Paul Magorrian (21) was shot dead by the British army in disputed circumstances in the St Malachy's estate in Castlewellan in August 1974.
While MLAs can only claim rent and rates for offices with signs bearing only the name of the elected representative, there are no such rules governing Westminster offices.
Mr Wells said Sinn Féin speaks of "reaching out to their Unionist neighbours whilst erecting a sign which will cause enormous offence to the families of the 70 innocent victims of terrorism in south Down".
"What makes this development even more appalling is that when he was elected as the MP for South Down, Hazzard promised that he would work for all the people of the constituency," he said.
"How could anyone who is not a republican feel comfortable going into a constituency office so obviously dedicated to two IRA terrorists?
"I have made separate complaints to the Commissioner for Standards at both Westminster and Stormont."
Speaking to BBC Talkback, Mr Hazzard described Mr Wells' comments as "hypocritical" saying the building has been named after Peter McNulty and Paul Magorrian since before he was born.
He said it was "absolutely fitting".
"They were killed in their area and their families are held in the highest regard," he said.
"I would also point out that less than 50 metres from this office there is a British war memorial to remember all those that gave their lives in a British uniform, some of whom in that uniform killed Paul Magorrian who was killed beside my office by a British soldier."
A Sinn Féin spokesman defended the naming of the advice centre, saying it was not a new development.
"The Sinn Féin advice centre in Castlewellan – which is currently being used as the constituency office by Chris Hazzard MP - has been named after Peter McNulty and Paul Magorrian for 25 years.
"Under the Good Friday Agreement, everyone, including Irish republicans, have the right to remember their dead with dignity and respect."
