Nato troops in eastern Europe ought to be "combat ready" to deter Russian aggression, Poland's ruling party chief, Jarosław Kaczyński, has said.

But he also defended his conservative views on homosexuals and Poland's judicial reforms in a turbulent weekend for Polish-EU relations.

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EU values commissioner Vera Jourová is in Warsaw this week (Photo: European Commission)

"He [Russian leader Vladimir Putin] only attacks where he sees weaknesses and sees a chance to win," Kaczyński, the chairman of Poland's ruling Law and Justice (PiS) party, told German newspaper Bild on Saturday (25 January).

"Russia finds it difficult to face massive resistance, even of a diplomatic nature. This certainly applies to Poland and the Baltic states. That is why Nato presence is so important here," he added.

"Germany should send more troops to the Baltic States ... Good combat and operational readiness is required in eastern Europe," Kaczyński said.

The PiS chairman rarely gave interviews.

But he spoke out to rebuke Putin for "misusing history for his politics" after the Russian leader recently accused Poland of starting World War 2 [WW2] and of colluding in the Holocaust.

"The world knows the truth: It was Stalin's Soviet Union that attacked Poland on 17 September 1939. It was Soviet soldiers and hangmen of the NKVD [secret police] who murdered hundreds of thousands of Polish officers in Katyń ... in 1940," Kaczyński said.

Poland is currently weighing up whether to seek WW2 reparations from Germany in a move that could further strain EU politics.

But Kaczyński also praised modern Germany by contrast to Putin's regime.

"Germany and Russia are not comparable! There is a democratically elected government in Berlin, where law and morality apply. This cannot be said of Russia," Kaczyński noted.

German WW2 transparency has also "made it really difficult for Russia and its president to continue telling lies and portraying us Poles in a bad light," he added.

Kaczyński spoke amid turbulent times also in Polish-EU relations.

EU institutions launched a sanctions procedure against Poland two years ago over allegations that PiS was undermining judicial independence.

The Polish constitutional court could no longer "give effective constitutional review", a European Commission spokesman also noted last Friday, while urging PiS to restore the court's "legitimacy".

That saw Polish deputy foreign minister Paweł Jabłoński summon the EU envoy to Warsaw, Marek Prawda, for a telling off on Saturday.

The EU statements were "seriously inconsistent" and based on "double standards", Jabłoński said.

They were a based on "a major misunderstanding", Kaczyński also told Bild, and the PiS judicial reforms were needed to purge "privileged groups" in Polish society who "originate from communist times", he added.

For her part, the EU commissioner for values, Vera Jourová, is in Warsaw on Monday to take part in a WW2 memorial prior to official meetings.

And she would continue to put pressure on Poland to respect EU norms, Prawda, the EU envoy, told Polish press.

"The European Commission is a community of law and cannot ignore the threats posed to [Polish] judges," he said on Saturday.

PiS values

The PiS has also clashed with the EU on migrants and on liberal mores more broadly speaking.

Kaczyński himself, in the past, has said African migrants brought "parasites and [dangerous] protozoa" to Europe and that homosexuality was a "threat".

He did not mention migrants on Sunday.

But he told Bild: "Whoever questions the traditional family model - the coexistence of men and women - is not only endangering Poland or Europe, but actually also the foundations of our civilisation".

Kaczyński claimed "there is no violence against homosexuals" in Poland, even though police arrested 25 people for attacking a pride march in one Polish town last July, for instance.

And he belittled EU support for the gay rights movement by suggesting it was a fake cause.

"I could ask another question: 'Is the EU also addressing violence against small men?'," Kaczyński said.