DUP Leader Arlene Foster says it “doesn’t bode well”, after questioning the Taoiseach’s claims about a new round of talks.
Leo Varadkar said negotiations to restore Northern Ireland’s power-sharing institutions could resume in the autumn.
However former first minister Ms Foster says she is not aware of any proposal, and has not been informed by the UK Government.
She said: “I have to say this doesn’t bode well, the fact that this is coming from Dublin, there’s nothing from London and none of the parties seem to know anything about it.
"I can only assume that Leo is jumping ahead and making comments about proposals but there's no firm commitment to talks on a particular date."
The Executive and Assembly at Stormont collapsed 19 months ago and multiple rounds of talks have failed to restore them.
Leo Varadkar stated that the UK and Irish governments would try to reconvene negotiations between local parties, potentially in October.
He said he believed there was an opportunity “certainly before the end of the year” to get the institutions up and running again.
“We would intend, in the autumn some time, trying again to get the parties in Northern Ireland together,” Mr Varadkar told reporters in Dublin on Tuesday.
In response, the UK Government said its and Secretary of State Karen Bradley’s “top priority remains the restoration of devolved government in Northern Ireland”.
Sinn Féin President Mary Lou McDonald said her party is ready for dialogue, but that the talks process needs to be “viable”.
She said: “We are a party of dialogue, we have always talked to others, we will always seek progress, but these talks, when they happen, have to be about delivery.
“We have no interest in talking around in circles, we need to be sure that the agreements that we have entered into will be honoured.
“The two governments need not simply to convene talks, they have to demonstrate that these talks are viable.”
One of the issues at the heart of the impasse is over Irish language rights.
Arlene Foster says the DUP’s long-standing stance has been that there can be no standalone Irish language act, and this remains the case.
“We have always said that that’s not a prospect,” she says.
“We have always been very clear that there would not be a standalone Irish Language Act, we’ve said it to Sinn Féin many times, we’ve said it to our own Government on many occasions as well so that’s the position of the DUP.”
Ms McDonald said she finds it “hugely disappointing” that Ms Foster and the DUP “don’t seem to have moved on one inch since last February”.
She added: “The rhetoric of ‘no, nay, never’ gets nobody anywhere.”