Copenhagen (AFP) - A Danish 'No' in a referendum on adopting EU rules on cross-frontier policing shows a growing chasm between the public and the establishment in the 28-member bloc, politicians and commentators said Friday.

Against the backdrop of Europe's refugee crisis, much of the debate on whether Denmark should give up its exemption on EU justice policies came to be about the wider issue of Copenhagen's ties with Brussels.

The 'Yes' side had advocated for international coordination in the fight against cross-border crime, including violent extremism.

But the 'No' camp won the Thursday referendum with 53.1 percent of the vote, an outcome the tabloid BT called "a gut punch for the elite".

Thursday's referendum was Denmark's seventh vote on its relationship with Europe since joining the EU in 1973.

The Danish vote is likely to have been closely watched by British Prime Minister David Cameron, who has promised to hold a referendum on the country's EU membership by the end of 2017.

On his way into an EU meeting on security issues, Belgian Interior Minister Jan Jambon said the Danish result was part of a wider trend.

In some European countries "people are becoming more critical. We have to be aware of this signal," he said.

Politicians across Europe faced "populist parties ... demanding the repatriation of powers from Brussels as the solution to problems," Josef Janning, of the European Council on Foreign Relations in Berlin, told AFP.

But political leaders should be open about Europe's growing integration and explain its benefits rather than trying to downplay it to voters, which "seems to have strengthened their suspicion that something is wrong with the EU," he said.

- Future uncertain -

By maintaining its exemption on justice rules, Denmark could have to leave the EU's law enforcement agency Europol as soon as next year as the legal status of the agency changes.

The 'No' side wants to negotiate a special agreement that would enable Denmark to stay inside Europol, which tackles organised crime, human trafficking and terrorism, but it is unclear how long that would take or if it is even possible.

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Much of the 'No' side's success was due to skilful campaigning by the eurosceptic, anti-immigration Danish People's Party (DPP), the right-wing Jyllands-Posten daily said.

"Although the party is the biggest in the right-wing bloc, it continued to benefit hugely from portraying itself as the antithesis of the elite," it said.

Left-leaning rival Politiken said there were several factors behind the outcome, such as the growing number of refugees and a "deep distrust of politicians."

Marlene Wind, a political science professor at the University of Copenhagen, echoed the charge that the 'No' side had mostly exploited "a lack of trust in politicians" and the EU.

"They simply appeal to this gut feeling that many voters have that this is just one big bureaucratic monster," she said.

- Better balance -

Prime Minister Lars Lokke Rasmussen admitted there was "considerable scepticism about the European project" among Danes, as he reflected on the outcome.

"We need common sense back. Most people can see that the single market is a good idea" but the bloc needed "a better balance," he said.

He underscored the need for a "strong EU where it makes a real, positive difference. A slimmer EU where the individual countries in a more meaningful way can solve the problems in their own way."

Voters seemingly wanted a stronger EU on issues like protecting the bloc's borders, but were also concerned over potential abuse of Denmark's social welfare systems by European workers, he said.

Denmark negotiated its exemptions on EU justice rules with Brussels in 1993 as a condition for accepting the Maastricht Treaty, which voters had rejected in a referendum the previous year.