The Fianna Fáil leader has said any suggestion that the abortion referendum is rigged is 'quite ridiculous'.
Micheál Martin says the claims from the No side do not have any basis.
The claims from the Save The 8th group came after Google announced it was to ban all ads related to the referendum.
Google, which also owns YouTube, said: "Following our update around election integrity efforts globally, we have decided to pause all ads related to the Irish referendum on the Eighth Amendment."
It followed Facebook's decision to ban all referendum-related ads from outside Ireland.
While Google's move was welcomed by the Together For Yes umbrella group, No campaigners slammed Google's decision.
Speaking earlier today, Save The 8th's John McGuirk said: "Who are we accusing of rigging the referendum? Government ministers, Yes campaigners and frankly a lot of journalists who've been putting immense pressure on these organisations."
However, Fianna Fáil leader Micheál Martin - who supports repealing the Eighth Amendment - has rejected that suggestion.
Fianna Fáil leader Micheál Martin addressing the Lawyers for Yes group. Says this campaign will have been one of the most debated ones in history by the end pic.twitter.com/ZYVtlWG6ox
— Sean Defoe (@SeanDefoe) May 9, 2018
Deputy Martin - who addressed the ‘Lawyers for Yes’ group this evening - observed: "We have a healthy parliamentary democracy - there are plenty of fora for people to articulate, and plenty of opportunities to engage with people and have conversations with people.
"We have a Referendum Commission, which I believe will give impartial and objective information to the public. So to suggest it's 'rigged' is quite ridiculous."
The opposition leader added: "I welcome the Google decision, and I think it will level the playing pitch. We've been doing that for quite a long time with broadcast - radio and television - in terms of advertising and not allowing it in the course of campaigns.
"It's an extension of that, and I think it perhaps safeguards the integrity of our referendum."
The Eighth Amendment referendum will take place in just over two weeks, on Friday May 25th.
Reporting by Sean Defoe and Stephen McNeice
