WARSAW (REUTERS) - Tens of thousands of protesters marched through the Polish capital on Saturday in one of the largest demonstrations in years to demand more jobs and higher pay, blaming Prime Minister Donald Tusk's government for failing to tackle unemployment.

The city council said about 100,000 people turned out for the march organised by trade unions, waving flags and blowing trumpets as they walked peacefully through central Warsaw.

The Polish economy has seen two decades of uninterrupted growth but narrowly avoided recession at the start of the year.

It has since shown signs of picking up but the recovery has been too weak to significantly bring down unemployment, especially among youths. The jobless rate stands at 13.1 per cent, after hitting a six-year high of 14.4 per cent in February.

"We have come to Warsaw to show a red card to the government," said Tomasz Danielewicz, 43, a nurse taking part in the march.

Unions are opposed to new legislation that gives employers more flexibility in determining the working hours of employees.

One of the banners carried by protesters read: "Part-time job, full-time exploitation".

"The government gets its last warning today. If it draws no conclusions, we will block the whole country, all roads and highways," Jan Guz, leader of the OPZZ union told demonstrators.

The economic slowdown has brought Tusk's government approval ratings to their lowest levels since he came to power six years ago, and opinion polls from recent weeks show his party has lost ground to the opposition.