Taoiseach Leo Varadkar has warned British prime minister Theresa May "just putting off" finding a solution to a hard Irish border until 2021 "isn't enough" to resolve the ongoing Brexit stand-off.
Speaking to reporters at the headquarters of the Orange Order in Belfast, Mr Varadkar said while Britain's suggestion all of the UK could remain in the customs union until 2021 is a "small step" in the right direction, the plan is still likely to be rejected by the EU.
Asked about the time-limited back-stop solution heralded by London as a major breakthrough before the European Council summit on June 27-29, Mr Varadkar said he welcomed the development as "we've been asking for months for something in writing".
However, rejecting claims it is a significant move by Britain, the Taoiseach said the potential policy still falls short of what is needed.
"First of all the paper produced by the British government yesterday is welcome, we've been asking for months for something in writing, I think it does represent a small step forward.
"We're now going to examine it, with the other member states, and really there are three questions we have to ask. One: does it achieve what we want it to achieve which is guaranteeing there is no hard border. Two: is it all weather. And three: does it respect the single market and customs union.
"It is a step in the right direction, it is welcome, but it does fall short and it falls short really on two accounts.
"One, it deals with the customs aspect of the border but not the regulatory aspect, and in fairness they accept that. And two, we do have a difficulty with any sort of deadline.
"The only deadline that should be in the back-stop is that all-weather if and when deadline the backstop should apply until such a time as there is a UK relationship that avoids a hard border.
"Just putting off a hard border for two or three years, or six years or 20 years, isn't enough," Mr Varadkar said.