On the eve of new Polish measures that could mean dozens of senior judges losing their jobs, the European Union has launched a legal case against the country's right-wing government.

The EU's executive has already accused the Polish authorities of bringing in laws that "interfere significantly" with the judiciary.

Now it has given Warsaw a one-month deadline to answer its concerns.

Under the laws, up to 40% of Supreme Court judges could be forced out.

The first president of the court, Malgorzata Gersdorf, could be among those pushed out before her six-year term ends, by a rule that brings down the retirement age from 70 to 65, the EU warns.

Why are the reforms so controversial?
Poland insists its reforms, which have already come into effect, are aimed at updating an inefficient system and replacing judges who date back to a communist era that collapsed in 1989.

The EU launched a legal case last December, arguing that the independence of the Supreme Court and Constitutional Court have been undermined by the package of reforms.

Now it has increased its pressure on Warsaw over a measure that comes into force on 3 July. All judges over 65 have been given until that date to ask President Andrzej Duda to prolong their mandates.

The president has the power to grant an extension. However, the EU complains that the judge has no way of seeking a review and the head of state does not have to explain any reasons for turning such requests down.

The EU's executive, the European Commission, has given Poland a month to respond. It normally gives two months. Foreign Minister Jacek Czaputowicz said the law was binding and "for the time being our stance is that we are right".