The Taoiseach has said he is not worried despite another poll which shows a downward trend for Fine Gael.
A Panelbase poll for The Times shows that Sinn Féin has overtaken Fine Gael to become the second most popular party.
The online survey of 1,000 people has Fianna Fáil in the lead on 23%, followed by Sinn Féin in second on 21% and Fine Gael trailing on 19%.
Leo Varadkar acknowledged those two rival parties are ahead of Fine Gael, but added that it is very tight just one week ahead of the General Election.
Speaking this afternoon, he said: "Well, it's one poll and it's an online poll done by a company that hasn't done polls in Ireland before.
"If it's correct, it would see both Fianna Fáil and Fine Gael losing seats in this election, which I think isn't something that anyone would have predicted a few weeks ago.
"There's another poll out this evening so let's see how that goes."
Mr Varadkar reiterated today that he would "never" go into government with Sinn Féin.
In a video posted on social media, prominent party members were asked if they would ever agree to join Sinn Féin after the election, to which each person said "no".
I will never go into government with Sinn Féin. I asked my team if they would and they answered unequivocally.
Micheál Martin cannot say the same about his front bench. pic.twitter.com/zEoKqpIgQO— Leo Varadkar (@LeoVaradkar) February 1, 2020
He also claimed that Fianna Fáil's Micheál Martin "cannot say the same about his front bench".
The Taoiseach pointed out that a number of Fianna Fáil TDs have already said they would consider a coalition with Mary Lou McDonald's party and that they were displaying "arrogance".
He said: "There's quite a growing list of Fianna Fáil people who are gearing up for coalition with Sinn Féin.
"I think there's an element of Fianna Fáil who think this election is in the bag for them.
"They're probably measuring up curtains, appointing advisors and talking about bringing back garda cars.
He added: "That's the kind of arrogance we see from Fianna Fáil and I hope they get a surprise next weekend."
However, Micheál Martin said it's still all to play for despite his party's lead in the latest opinion poll.
He said: "You remember the first opinion poll, and I said there would be any more and they would vary.
"As far as I'm concerned, there's still a lot to play for; people are still making up their mind.
"What is absolutely clear is that there is a clear desire for a change, for a change in government, and that's very strong."
'They need to grow up'
Meanwhile, Sinn Féin's Director of Elections Pearse Doherty accused Fine Gael and Fianna Fáil of resorting to "desperation tactics" in "trying to outdo themselves in attacking" his party on the last weekend before voting.
He said: "They are under the cosh and resorting to desperation tactics. I think they need to grow up.
"They have spent this campaign making a whole lot of noise but not a whole lot of sense.
"People know exactly what the establishment parties will do in government - more of the same."
Elsewhere, the Green Party launched its housing policy today.
They are calling for over 20,000 homes to be built on public lands in Dublin City which are currently controlled by Nama and Dublin City Council.
