Warsaw (AFP) - The powerful head of Poland's governing conservatives, Jaroslaw Kaczynski, has accused Germany of "rejecting" its World War II responsibilities, going as far as to suggest Berlin should pay reparations.

"We are talking about huge sums and also the fact that the Germans have for years rejected their responsibility for World War II," said Kaczynski, who has several times made controversial remarks about Warsaw's neighbour.

Kaczynski made his comments during a talk late Thursday with listeners of Catholic radio station Radio Maryja.

One of Kaczynski's chief bugbears is the recently opened Museum of the Second World War in the port city of Gdansk.

He described the museum as "nothing other than a kind of present" from European Council president, former Polish premier and Gdansk native Donald Tusk to German Chancellor Angela Merkel.

"It is a museum which subscribes to German historic policy," Kaczynski insisted.

The museum has made waves in that it offers visitors a view of World War II which the nationalist government feels is not Polish enough and does not highlight patriotic resistence to Nazi occupation.

The museum has been the focus of a legal battle after the government sought to unite it with another in Gdansk.

Noting that move had faced a legal challenge, Kaczynski complained at seeing "human rights defenders complain to the courts (who) order the changes be overturned," referring to civic rights spokesman Adam Bodnar.

Quite aside from the controversy surrounding the museum, Kaczynski saw that legal battle as illustrative of the government's standoff with the courts in general.

The relationship between the government and the judiciary is in the headlines after President Andrzej Duda on Monday surprisingly vetoed two controversial court reforms amid popular protests and EU rumblings of concern.

His decision, which Kaczynski called as "a very serious mistake," infuriated the ruling Law and Justice (PiS) party, whose policies Duda had previously rubber stamped.

Kaczynski has previously claimed in a book that Germany had ambitions on restoring "imperial" power and also criticised Merkel over her immigration policy which saw Germany take in more than one million migrants last year.

In his Thursday comments he suggested Polish diplomats should stand up to Berlin but charged that "for that you need diplomacy which is effective and loyal to the state."