TUV leader Jim Allister has said Mary Lou McDonald's attendance at a commemoration for an IRA bomber shows that nothing will change in Sinn Fein under her leadership.
Mr Allister was speaking after the party's president-elect was present at a wreath-laying ceremony in Castlewellan, Co Down, for an IRA member who died when the device he was planting at the town's police station exploded prematurely.
Ms McDonald, along with South Down MP Chris Hazzard and Newry and Armagh MP Mickey Brady, attended the commemoration on Friday.
Wreaths were laid and a piper played a lament to mark the 46th anniversary of the death of Peter McNulty.
The 47-year-old, a member of the IRA's South Down Brigade, died in the attack on January 26, 1972.
Mr Allister said: "Here we have Mary Lou McDonald and two Sinn Fein MPs glorifying a terrorist bomber who sought to bring death and destruction to Castlewellan.
"Just over a week on from all the cant about respect, following the Kingsmill video PR disaster, usual service has been resumed with the glorification of terrorism still a top priority."
The TUV leader said those who predicted that Ms McDonald's leadership would mark a break with the past had been quickly proved wrong.
"One of her first acts as Sinn Fein president-elect is standing in public to honour and venerate a terrorist," he said.
"The narrative we were spun was one of new beginnings and fresh faces and fresh starts. We can now see the sincerity of that.
"Mary Lou McDonald is entirely happy to commemorate someone who was part of a terrorist unit who met his end at his own hands."
He called on the DUP to carefully consider the attendance at the event by the Sinn Fein leader-in-waiting.
"Those who are trying to placate Sinn Fein at the current talks in Stormont urgently need to pay attention. Nothing has or will change in that party. Ultimate control in the republican movement lies with the military wing," he said.
Last February Sinn Fein Northern leader Michelle O'Neill angered unionists when she was the main speaker at a 25th anniversary commemoration for four IRA men in her home village of Clonoe, Co Tyrone.
They were shot dead by the SAS in 1992 when they were ambushed after an attack on Coalisland RUC station.
Unionists and IRA victims said her presence at the event undermined her pledges to work for reconciliation.
But Mrs O'Neill said nobody should have been surprised at her attendance.
"I am a republican, that's not a secret," she said.
"I did know these young fellas personally and I know their families and friends and I know the community they came from.
"Everybody has a right to remember their dead no matter who you are or what your political perspective is.
"We all have a different narrative, and we'll always have a different narrative, and people have a different perspective on the past."
McNulty was the first IRA man to be killed in Co Down during the Troubles. A farmer from Burrenreagh, near Castlewellan, he died when the 15lb device he was planting exploded prematurely near the police station's perimeter gate.
A second IRA man was badly injured in the blast. Around 2,000 people attended McNulty's funeral in Bryansford.
His coffin, draped with the tricolour and with military gloves and a black beret on top, was flanked by 20 women wearing black scarves. Local youths from Na Fianna Eireann formed a guard of honour at the church.
In the graveyard members of the IRA's South Down Brigade emerged from the crowd and fired a volley of shots over the coffin.
McNulty had previously been involved in 'Operation Harvest', the IRA's 1956-62 border campaign.
Local republicans said he had played a "key role" in networking IRA units across south Down "as well as engaging in attacks on selected targets along the border". After the border campaign ended he continued to be involved in republican politics.
The IRA attack on Castlewellan police station followed a security force clampdown on an anti-internment march from the town to Newcastle three days earlier. Rubber bullets had been fired and more than 40 people arrested.