Andrej Plenkovic, the Prime Minister of Croatia, told the European Parliament the bloc “must maintain unity in the process of Brexit negotiations” for the project to survive unscathed.
Mr Plenkovic was setting out his vision for the EU for 2020, when Croatia takes on the rotating presidency of the European Council.
He blamed the “bad decision” of Brexit as a “result of populism”, while Croatian MEP Reza Tomasic said the EU will not fulfil its potential if the bloc’s largest countries are allowed to “impose their will” on the small ones.
But Mr Henkel has said the loss of Britain in the common market can be not compensated by smaller nations stepping up.
The German MEP said: “The Prime Minister of Croatia rightfully mentioned the importance of the common market and President Juncker said that Croatia is both an example an inspiration for Europe.
“Well, Brexit is a disaster for the common market and an example of desperation in Europe.
“Economically, Brexit is the same as Croatia and the other smaller 18 countries leaving the EU at the same time.”
Mr Henkel is one of the architects behind the ‘New Deal for Britain’ movement, alongside leading figures from German business, urging the European Union to offer the UK a last-ditch deal in a desperate bid to stop Brexit.
He added: “I urge the Croatian Prime Minister to push for the Council and the Commission to offer a new deal for Britain because of the clear negative impact Brexit will have on Croatia, amongst others.”
The German concluded that a new deal must “support the growing number of British citizens who regret Brexit and avoid the biggest disaster for the European Union”.
There is currently “some divergence” between the UK and EU’s when it comes to negotiating a deal for the transition period, according to Michel Barnier.
The European Commission’s chief Brexit negotiator declared the “time had come” for the UK to choose what it wanted after its March 2019 exit.
Brexit Secretary David Davis said the UK’s position was “perfectly clear”.
He added: “We have already published a great deal about our proposals, in terms of what the customs arrangements will be, what the other arrangements will be with respect to being outside the Union.
“We have said in terms we want a comprehensive free trade agreement and we want a customs agreement and to make that as frictionless as possible, to make as much trade as currently exists as free as possible, while still giving ourselves the opportunity to make free trade deals with the rest of the world… It is perfectly clear what we want to do.”