The president of the European Council has told of how Brexit makes him “furious” and might be “one of the saddest moments” in recent European history.

In a speech in Dublin Donald Tusk said Britain’s departure from the EU was diverting him from concentrating on more European integration and instead had left him “dealing with disintegration” and taking part in a damage control exercise.

“I don’t like Brexit. Actually, that’s an understatement,” he told an audience at the University College Dublin Law Society, where he was receiving an honorary lifetime membership.

“I believe Brexit is one of the saddest moments in 21st century European history – in fact, sometimes I am even furious about it.”

He added: “This year will be about Brexit mainly, unfortunately. It means that instead of further integration I will be dealing with disintegration, in fact.

“By this I mean some kind of damage control process, and my main focus will be to eliminate, or at least to reduce the negative side effects of Brexit, with the Irish question, of course, at the centre of my attention.”

Mr Tusk contrasted his host country of Ireland with its neighbour Britain, saying that despite Ireland taking proportionally more EU immigrants than the UK it had raised relatively few problems or concerns about immigration. He spoke at length about the bond he saw between his native Poland and Ireland, stating that “nobody celebrates a defeat as beautifully as the Irish and the Poles, and history has given both of our countries quite and few opportunities for such celebrations”.

In a question and answer session following the speech, Mr Tusk said he did not have “grand visions” for the future of the European Union but instead that “the most important thing in politics is to always try to achieve what is possible”.

“I think today we need to be more cautious with dreams and more effective when it comes to acts,” he added, warning that his audience should be aware of “how little time is needed to undermine and demolish this structure” of European unity.

What is still needed to complete a deal with the EU?

In his last speech in Ireland at the start of the year, Mr Tusk had said there could be no progress on other Brexit issues until the issue of the Irish border was dealt with – just days before the European Council signed off progress on a transition period while leaving the Irish border issue unresolved.

Both sides of Brexit talks are now locked in intense negotiations about the Irish border, with the EU hoping for progress by June.

Brexit threatens life on the Irish border: in pictures Show all 15 1 /15 Brexit threatens life on the Irish border: in pictures Brexit threatens life on the Irish border: in pictures An abandoned shop is seen in Mullan, Co Monaghan. The building was home to four families who left during the Troubles. The town was largely abandoned after the hard border was put in place during the conflict. Mullan has seen some regeneration in recent years, but faces an uncertain future with Brexit on the horizon Reuters Brexit threatens life on the Irish border: in pictures A defaced ‘Welcome to Northern Ireland’ sign stands on the border in Middletown, Co Armagh Reuters Brexit threatens life on the Irish border: in pictures Mervyn Johnson owns a garage in the border town of Pettigo, which straddles the counties of Donegal and Fermanagh. ‘I’ve been here since 1956, it was a bit of a problem for a few years. My premises has been blown up about six or seven times, we just kept building and starting again,’ Johnson said laughing. ‘We just got used to it [the hard border] really but now that it’s gone, we wouldn't like it back again’ Reuters Brexit threatens life on the Irish border: in pictures Farmer Gordon Crockett’s Coshquin farm straddles both Derry/Londonderry in the North and Donegal in the Republic. ‘At the minute there is no real problem, you can cross the border as free as you want. We could cross it six or eight times a day,’ said Crockett. ‘If there was any sort of obstruction it would slow down our work every day’ Reuters Brexit threatens life on the Irish border: in pictures John Murphy flies the European flag outside his home near the border village of Forkhill, Co Armagh Reuters Brexit threatens life on the Irish border: in pictures Potter Brenda McGinn stands outside her Mullan, Co Monaghan, studio – the former Jas Boylan shoe factory which was the main employer in the area until it shut down due to the Troubles. ‘When I came back, this would have been somewhere you would have driven through and have been quite sad. It was a decrepit looking village,’ said McGinn, whose Busy Bee Ceramics is one of a handful of enterprises restoring life to the community. ‘Now this is a revitalised, old hidden village’ Reuters Brexit threatens life on the Irish border: in pictures Union Flag colours painted on kerbstones and bus-stops along the border village of Newbuildings, Co Derry/Londonderry Reuters Brexit threatens life on the Irish border: in pictures Grass reflected in Lattone Lough, which is split by the border between Cavan and Fermanagh, seen from near Ballinacor, Northern Ireland Reuters Brexit threatens life on the Irish border: in pictures Donegalman David McClintock sits in the Border Cafe in the village of Muff, which straddles Donegal and Derry/Londonderry Reuters Brexit threatens life on the Irish border: in pictures An old Irish phone box stands alongside a bus stop in the border town of Glaslough, Co Monaghan Reuters Brexit threatens life on the Irish border: in pictures Billboards are viewed from inside a disused customs hut in Carrickcarnon, Co Down, on the border with Co Louth in the Republic Reuters Brexit threatens life on the Irish border: in pictures Seamus McQuaid takes packages that locals on the Irish side of the border have delivered to his business, McQuaid Auto-Parts, to save money on postal fees, near the Co Fermanagh village of Newtownbutler. ‘I live in the south but the business is in the North,’ said McQaid. "I wholesale into the Republic of Ireland so if there’s duty, I’ll have to set up a company 200 yards up the road to sell to my customers. I’ll have to bring the same product in through Dublin instead of Belfast’ Reuters Brexit threatens life on the Irish border: in pictures A disused Great Northern Railway line and station that was for customs and excise on the border town of Glenfarne, Co Leitrim Reuters Brexit threatens life on the Irish border: in pictures Alice Mullen, from Monaghan in the Republic of Ireland, does her shopping at a former customs post on the border in Middletown, Co Armagh. ‘I’d be very worried if it was a hard border, I remember when people were divided. I would be very afraid of the threat to the peace process, it was a dreadful time to live through. Even to go to mass on a Sunday, you’d have to go through checkpoints. It is terribly stressful,’ said Mullen. ‘All those barricades and boundaries were pulled down. I see it as a huge big exercise of trust and I do believe everyone breathed a sigh of relief’ Reuters Brexit threatens life on the Irish border: in pictures A bus stop and red post box stand in the border town of Jonesborough, Co Armagh Reuters

Ireland’s EU commissioner Phil Hogan rubbished Theresa May’s plan for a “global Britain” trading with the world after Brexit on Monday, warning that there are “stubborn facts that over-shadow a rosy picture” painted by the prime minister.