The call by Fabian Zuleeg, chief executive of the Brussels-based European Policy Centre, comes with the fallout from the EU referendum vote yet to fully trickle through.
On Tuesday, a UK government spokesperson confirmed that the UK will not begin formal Brexit talks before the end of the year, saying, "The government's position has not changed. Article 50 will not be invoked before the end of the year."
Even so, Iain Duncan Smith, the former UK Secretary of State for work and pensions, and leading Brexit campaigner, has urged UK Prime Minister Theresa May to begin formal Brexit negotiations as "soon as possible."
He warned; "We shouldn't wait to see the outcome of the two elections in Germany and France (in 2017) - that suggestion is yet another attempt to turn this referendum result into a 'neverendum,' …Let us leave as soon as possible, so that we can get on and make the most of our new found independence."
Writing in the Guardian newspaper, Zuleeg partly agreed, saying that failure to trigger article 50 now will leave the EU in "limbo" and "clog up" its decision making processes.
He said, "There is still virtually nobody in Brussels who thinks that Brexit is a good idea, for the UK or for the rest of the EU. But decision-makers are now accepting this unpalatable reality and there is a growing impatience for the process to begin in earnest.
"There was some understanding for the UK's desire for a delay in the immediate aftermath of the referendum, recognising that it had carried out no contingency planning for a Leave vote.
"But now, with a new British government in place, many in Brussels believe it is time for the UK to formulate its goals and formally start divorce proceedings by triggering article 50."
Zuleeg, whose organisation is one of the leading think tanks in Brussels, believes the UK faces two options: the Norway model with access to the single market, and the Canada model, a trade partnership but outside the single market.
He went on, "The different options the UK has have very different implications - the Canada option implies no financial contributions, while the Norwegian option would mean a substantial continuing cost to the UK.
"In fact, given that Britain's budget rebate would no longer apply, once the UK is out of the EU, Britain could end up paying more to Brussels."
Zuleeg believed that in the upcoming Brexit talks, the UK will seek to "have its cake and eat it", but insisted that "that is not acceptable to the EU."