The French presidential hopeful Marine Le Pen is to headline a European gathering of Eurosceptic and far-right leaders in Germany on Saturday as they seek to present a united front in a year of high-stakes elections.

Organisers of the conference in Koblenz, billed as a “counter-summit”, said participants would set out their joint “vision for a Europe of freedom”.

Authorities in the central German city are bracing for a large protest later on Saturday by a coalition of leftwing groups, mainstream political parties and unions. More than 1,000 police officers have been deployed to keep the demos peaceful.

Gathering under the banner “Koblenz stays colourful, no room for rightwing populism”, the demonstrators say they plan to play a rendition of Beethoven’s Ode to Joy, the EU’s anthem, outside the conference venue.

The conference has already caused controversy after organisers banned many news organisations from attending on the basis that they had “not met journalistic standards in past reporting”, the German newspaper Die Welt said.

The German broadcaster ARD has threatened to sue over its exclusion. Its programme director, Volker Herres, condemned what he described as a “massive encroachment” against the freedom to report.

He said: “It is a loss for our audience that we won’t be able to report on the meeting of rightwing populist parties in Europe. This gathering is of great importance for the future political course of this movement.”

Le Pen, the leader of France’s Front National, will share the stage with Frauke Petry, of the anti-immigration Alternative for Germany (AfD), Geert Wilders, of the Dutch anti-Islam Freedom party, and Matteo Salvini, of Italy’s anti-EU Northern League.

All are members of the Europe of Nations and Freedom group in the European parliament, which has 40 members from nine countries.

Wilders announced his attendance at the conference on his Twitter feed using the hashtag #WeWillMakeOurCountriesGreatAgain, a play on the new US president Donald Trump’s slogan “Make America great again”.

Wilders’ party could win the largest percentage of the vote in the Dutch parliamentary election on 15 March. Le Pen is among the top contenders in France’s presidential vote in April, and AfD hopes to enter the German parliament in September.

“The aim is to outline the Europe of tomorrow,” Le Pen told the French radio station Classique on Friday. “Each of us is strongly attached to sovereignty and freedom in general. I believe that is what also brings us together is a rejection of the European Union’s laissez-faire policies.”

She said none of the participants could be described as extreme right, a label that she said was used “by our adversaries to discredit us”.

Timo Lochocki, a political analyst with the German Marshall Fund, told Agence France-Presse the gathering was mainly “just good PR”, given that the parties had little to gain from strengthening ties.

“This is largely to increase media attention,” he said. “The reasons why people vote for these parties are purely national and are independent from any alleged cross-national cooperation between the far right.”