Poland's government on Thursday estimated the financial cost of World War II losses to be 1.3 trillion euros (dollars) and said it would "ask Germany to negotiate these reparations".

"It is a major sum of 6.2 trillion" zloty, Deputy Prime Minister Jaroslaw Kaczynski, head of the ruling Law and Justice party, said, adding that receiving reparations would be a "long and difficult" process.

Kaczynski was speaking at a conference dedicated to the presentation of a report on Poland's losses in the 1939-1945 war.

Since coming to power in 2015, Poland's governing Law and Justice (PiS) party has often championed the issue of war reparations. 

Work on the reparations report began in 2017 when the conservative government insisted that Germany had a "moral duty" in the matter.

Germany has often rejected Poland's claims, pointing to a 1953 decision by Poland to renunciate reparation claims against East Germany.

On Thursday, Kaczynski brought the issue back to front and center.

"We have not only prepared a report... but we have also taken a decision, a decision on further action," Kaczynski said.

"That action is to ask Germany to negotiate these reparations. And this is a decision that we will implement," he added.

"The Germans invaded Poland and did us enormous damage. The occupation was unbelievably criminal, unbelievably cruel, and caused effects that in many cases continue to this day," the PiS president said.

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Germany FM: The issue of reparations to Poland is "closed" 

Poland's World War II reparations are "closed," according to a spokesman for the German Foreign Ministry cited by RIA Novosti, and Germany's attitude toward them is unaltered.

"The position of the federal government is unchanged, the issue of reparations is closed. Poland refused further reparations a long time ago, in 1953, and repeatedly confirmed this refusal. This is a necessary basis for today's European order," the spokesman said.

He continued by saying that Germany was still morally and politically accountable for World War II.