The Taoiseach was today accused of double standards after he ruled out ever having Sinn Féin as a coalition partner.
Democratic Unionist MP Nigel Dodds warned Mr Ahern not to expect his party to stomach in Northern Ireland what he would not accept in the Republic.
In comments to the Sunday Independent, Mr Ahern said he would lead Fianna Fáil into Opposition rather than consider going into a coalition government with Sinn Féin.
"Even a radical overhaul of Sinn Fein economic policy would have little real credibility after 35 years of Marxism," the Taoiseach said.
"I believe Sinn Féin are agents of poverty and disadvantage. I believe the very notion of Sinn Féin in government would lead to a flight of investment, which is untenable in a small open economy.
"For the good of the country, we cannot accept those policies in government. A practical republican programme delivering real benefits for ordinary people would be impossible with Sinn Féin in government.
"In such circumstances, I would lead my party into Opposition rather than contemplate coalition with Sinn Féin or an arrangement for their support in government."
With unionists facing pressure to resume power-sharing in Northern Ireland featuring Sinn Féin, the DUP said Mr Ahern's comments were another example of double standards by the Government.
"Bertie Ahern has ruled out in categorical terms any prospect of Sinn Féin in government," the North Belfast MP said.
"Is it too much to expect that double standards will not apply once again ?
"Unionists have learned that consistency and morality long ago ceased to be the benchmarks of this political process as far as the (British and Irish) governments are concerned.
"I have little doubt that the same Bertie Ahern will be at the forefront of pressure from Dublin on unionists to accept what they will not."
He continued: "Now that Dublin is facing up to the reality of what it means to have Sinn Féin in government, let there be no further double-talk from Dublin or London.
"Unionists in Northern Ireland will not be pushed over as they were when (former UUP leader David) Trimble negotiated for them.
"Nor will the DUP accept second class standards for the people of this province."
PA