The Fianna Fáil leader has accused the Social Protection Minister of telling untruths and engaging in fake news.
It is in response to Leo Varadkar's 'welfare cheats' campaign which the minister says has seen savings of over half a billion euro.
Micheál Martin says the actual fraud savings are far less.
"Deputy Willie O'Dea has tabled a parliamentary question, we got a comprehensive reply yesterday and that reply says, lo and behold, only 41 million is attributed to fraud in terms of payments.
"That social welfare inspectors do face-to-face interviews and desktop reviews and so on, it's an extraordinary degree of fake news that we've been a victim of," he said.