Updated

German public broadcaster ARD says it may take legal action after being refused access to a conference of European nationalist leaders later this month.

Volker Herres, ARD television's program director, tweeted a statement Thursday saying the broadcaster's editors "condemn this massive encroachment against the freedom to report."

ARD said it was denied accreditation by Alternative for Germany, an anti-immigration party that is doing well in opinion polls ahead of the country's fall general election. The station rejected the claim it had reported unfairly on the party in the past.

Apart from Alternative for Germany co-leader Frauke Petry and the party's European Parliament member Marcus Pretzell, French National Front leader Marine Le Pen and Geert Wilders of the Dutch anti-Islam Party for Freedom are expected to be at the Jan. 21 conference in Koblenz.