Former British deputy prime minister Nick Clegg has described as "illogical nonsense" the approach the UK is taking in relation to a border between Northern Ireland and the Republic.

Speaking on RTÉ’s Today with Sean O'Rourke, Mr Clegg said the border of a country that is inside a customs union and a neighbour that is outside, could not be administered without having meaningful checks in place.

He said the UK government's talk of attempts to avoid a hard border is just rhetoric, adding that in his view, the UK has chosen to leave the EU in the most uncompromising way possible by quitting both the single market and the customs union.

"You cannot administer a border between a country which is inside a customs union and a neighbour that is outside it without having meaningful checks at the border," said Mr Clegg.

"It is illogical nonsense. I think why the UK government is being so foolish on all of this is that they are trying to have their cake and eat it.

"They claim that you can somehow create a border and yet not have a border," he said.

Meanwhile, the Minister for Finance Michael Noonan has rejected any suggestion that the wrong message was sent by EU member states holding small group meetings ahead of the Brexit negotiations, such as the one Enda Kenny is attending in The Hague today.

The Minister said that ultimately the EU-27 would all speak with "one voice" and that would be the "European voice".

He said the purpose of the smaller meetings "on the side" was so that countries who had similar interests, unique to them, could agree a common position ahead of the negotiations.

This would then enable the EU negotiation team to "speak with a more informed voice".

He said it was a "pre-negotiation" and reinforced the fact that it would be the EU-27 together on one side of the Brexit talks, and the UK as the only negotiator on the other side.