The Sinn Féin leader says the party won't be entering into a confidence and supply agreement with either Fine Gael or Fianna Fáil.
It comes as the latest Ipsos/MRBI poll for the Irish Times put Mary Lou McDonald's party as the most popular party in the country.
The poll put the party at 25%, up four, while Fine Gael's support has slipped again to 20% while Fianna Fáil is also down 2 points to 23.
Ms McDonald says confidence and supply is fundamentally wrong.
She said: "The situation we have for example now with Fianna Fáil, where Micheál Martin wanted to take all of the credit for things that might have been considered good, but wants to dodge any of the responsibility or accountability for chaos in housing, chaos in health.
"I think there's something fundamentally dishonest in that. I think if you're in government, you're in government.
"So confidence and supply is not something that we are not will consider at all. That's off the table."
In a poll released this morning, Ms McDonald was ranked as the "most effective communicator" among party leaders during the election campaign to date.
A question put to the public asked: Which of the main party leaders do you believe has best communicated to voters during the campaign to date?
Ms McDonald came out on top with 32%, ahead of Fine Gael's Leo Varadkar on 15% and Fianna Fáil's Micheál Martin on 14%.