Speaking in the Irish parliament, Mr Varadkar said: "I don't know if Mr Corbyn will rise to the occasion, whether he will show leadership and be able to come up with a compromised plan with Prime Minister May".
"We need to be open to any proposals that she may bring forward to us", adding that as things stood Britain was heading towards a no-deal exit.
"The EU can not be held hostage to the resolution of a political crisis in the United Kingdom on a long-term basis", Macron said, adding that granting Britain a lengthy extension of the deadline for leaving the bloc was "not a certainty".
The comments underline growing frustration in Paris about the Brexit process, which has diverted attention away from pro-European Macron's plans for reinforcing the bloc.
He said the cabinet would meet this evening to discuss Brexit once the Taoiseach returned from his meeting with French president Emmanuel Macron in Paris.
The minister was referring to meetings that had begun at official level with the European Commission on how to manage the border in a no-deal Brexit, Reuters said.
But differences are emerging between the two sides as the possibility of a "no deal" Brexit looms, which would lead to the creation of a border between the United Kingdom territory of Northern Ireland and Ireland.
That becomes an even more hard task in a no-deal Brexit as Dublin has also pledged to maintain the integrity of the EU's single market, where goods move freely around the bloc without the need for checks.
But Ireland has been steadfast in refusing any reintroduction of a physical border, which was removed as part of a peace agreement reached in 1998 to end decades of conflict on the island.
Pressed for more detail, he replied: "A lot of it will depend on the approach the United Kingdom takes and whether they will cooperate with the possibility of checks happening at the ports in Northern Ireland".
Mr Macron, meanwhile, insisted the European Union will never abandon Ireland.
"We in Border Communities Against Brexit have a clear message, (Northern Ireland) voted to remain and we support the withdrawal agreement".