Thousands of judges and lawyers have taken to the streets in unprecedented protests against Nicolas Sarkozy, paralysing the legal system and shutting down almost all France's courthouses this week.

Magistrates' unions have for days expressed outrage at the president by hearing only urgent cases, after the president used a shocking murder case to attack judges for being too lax.

The gruesome Laetitia case gripped France after a teenage waitress disappeared one night after her shift in western France. Her severed limbs and head were found in the waters of an abandoned quarry after a lengthy search, but the rest of her remains have not been recovered. The suspect, a 31-year-old, refused to co-operate with the search or the inquiry. Recently out of prison after completing a sentence, he had 15 previous convictions.

The case struck a chord with Sarkozy's longrunning campaign to appeal to the rightwing vote by cracking down on repeat offenders. Sarkozy publicly branded the suspect "presumed guilty", slammed judges for incompetence and making mistakes after his prison release, and said: "Our duty is to protect society from these monsters."

Judges were furious that Sarkozy would declare a suspect guilty before either a trial or the end of investigations. They accused him of using the case to boost his "tough on crime" image ahead of what will be a tough race for presidential re-election next year.

"It's an old habit of his, using people's legitimate feelings of outrage ... for ends that are clearly electoral and demagogical," said Nicolas Leger, national secretary of the USM magistrates' union.

Sarkozy, a former lawyer, has been in a long standoff with France's magistrates, who have accused him of meddling in the justice system and planning reforms that threaten their independence.

The latest protests against political interference in the law are unprecedented in their scale. Judges took to the streets in dozens of French cities and towns, including Lyon, Bordeaux and Versailles. Outside the court of justice in Paris, more than a thousand judges and lawyers in robes gathered with placards and megaphones. Across France, their protests were joined by prison officers and police unions, until now traditionally supportive of Sarkozy, a former interior minister.

The judges are also complaining of a chronic shortage of staff and funding – one recent study found France spends less per inhabitant on the justice system than Azerbaijan or Armenia. The newsweekly Le Nouvel Observateur published extracts from the suicide note of an experienced magistrate who said he was taking his life because he could no longer work under the harsh conditions. One newspaper poll found 65% of French people support the judges' protests.

Sarkozy, whose popularity ratings are stagnating at about 34%, was preparing to try to win back some public support tonight with a long-scheduled and stage-managed "meet the people" TV appearance. Faced with a panel of handpicked members of the public, he was due to answer questions on the economy, unemployment and the "main worries of the French people".

The president is also facing outrage over conflicts of interest highlighted by ministers' luxury holidays in countries led by questionable regimes. He has said ministers should holiday in France.