Poland's government today estimated the financial cost of World War II losses to be €1.3 trillion and said it would "ask Germany to negotiate these reparations".

Deputy Prime Minister Jaroslaw Kaczynski, head of the ruling Law and Justice party, said it is a "major sum of 6.2 trillion" zloty.

He added that receiving reparations would be a "long and difficult" process.

The German government swiftly rejected Poland's call for reparations.

A foreign ministry spokesman stated in an email to AFP: "The German government's position is unchanged, the reparations issue is closed."

He pointed to a 1953 decision by Poland to renunciate reparation claims against East Germany which he called a "significant foundation for Europe's order today".

Mr Kaczynski had been 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.

Poland's Deputy Prime Minister Jaroslaw Kaczynski (file image)

Deputy Prime Minister Kaczynski today brought the issue back front and centre.

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

It comes as Poles today marked the 83rd anniversary of the outbreak of World War II in their country.

The Battle of Westerplatte was the first clash between Polish and German troops during the German invasion of Poland on 1 September, 1939, and thus the beginning and the first battle of World War II.