Taoiseach Enda Kenny has formally refused a second invitation to debate the European fiscal treaty with Sinn Fein leader Gerry Adams.
With just over two weeks until referendum day, the Taoiseach turned down TV3's latest offer for the live television broadcast.
Sinn Fein deputy leader Mary Lou McDonald said: "It is very telling that Mr Kenny is running away from this debate. He obviously does not want to debate the consequences of austerity and cutbacks for the Irish people."
The Taoiseach turned down TV3's first invitation last week, saying he would not take part in any programme involving veteran broadcaster Vincent Browne.
The debate moderator offered to step aside from the show, given the public interest in seeing the leader of the "Yes" campaign go head-to-head with a senior "No" campaigner.
Despite the station's political correspondent Ursula Halligan being drafted in as a replacement, the Taoiseach has insisted he will not take part.
Ms McDonald claimed Mr Kenny was worried that he will not come out of it well.
"There's an expression that says you can run, but you cannot hide," she said. "He may be running, but he can't hide from this treaty and its consequences."
Mr Kenny refused to participate in a TV3 debate in the run-up to last year's general election due to bad blood between himself and Mr Browne.
A Government spokesman confirmed that the Taoiseach had turned down TV3's latest offer and that he would inform the station in writing.