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 accused Mr Kenny of running from the consequences a Yes vote victory the referendum would bring.
"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," she said.
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 formally inform the station in writing.
Meanwhile, Mr Kenny came under further fire from the opposition today when Fianna Fail's Michael McGrath said he needed to develop thicker skin.
The party's finance spokesman said the Taoiseach had behaved disrespectfully towards a member of the public in Athlone yesterday when he told him he looked like he could do with a day's work. The man was one of a number of protesters challenging Mr Kenny on septic tank and household charges.
"I think that was very disrespectful," said Mr McGrath.
"All of us in politics have to understand that people are really hurting at the moment."