Politicians are due to meet next month to discuss a set of suggestions of how to deal with criminals who have served their prison sentences but are considered to pose a continuing threat to the public, after Germany’s high court ruled that so-called preventive detention was unconstitutional.

The idea is to replace the ‘pure’ version of preventive detention with a therapy-based ‘treatment detention’.

In a serious split between the German Police Union (DPolG) and the ministry, the union’s chairman Rainer Wendt criticised Leutheusser-Schnarrenberger personally, for going on holiday rather than staying at work to solve the preventive detention problem.

The Constitutional Court ruled in May that the practice of keeping dangerous criminals in prison after their original sentences are served could not be continued, backing a previous ruling from the European Court of Human Rights which said in January that the German system breached the European Convention on Human Rights.

Politicians have been given until the end of May 2013 to set up a new system, while those criminals held under current rules must be released unless there is a very high risk they will commit serious violent or sexual crimes.

Wendt told the Passauer Neue Presse that the minister responsible was going on holiday while released criminals were able to attack children.

“Things are being endlessly debated and argued and the victims are left with nothing. I have no understanding for the blockade of the FDP,” he said, referring to Leutheusser-Schnarrenberger’s Free Democratic Party.

Police forces are under enormous pressure to protect the public from the violent and sexual criminals being released – often setting four or five officers to follow them at close quarters around the clock. This practice is also controversial, with critics saying it effectively identifies the criminals, who have served their sentences, and quashes any realistic chance they may have of rehabilitating.

Wendt said this cost enormous amounts of police manpower and that it was up to politicians to solve the problem. He repeated his demand for sex criminals and their location to be identified online.

“Parents must be able to protect their children,” he said, while dismissing any fears of vigilante justice.

But Leutheusser-Schnarrenberger said there was no way such a scheme would be adopted in Germany. “Public pillories are not compatible with the rule of law,” she said.

“It does not help to prevent violence if neighbours raise a group against a released prisoner.” She said this would only create even more work for the police.

She said the government and the federal states would work quickly to agree new regulations for dangerous criminals, suggesting that the two-year window set by the constitutional court would be more than enough time.

The other police union, the Union of Police (GdP), has taken a more measured tone, but also warned that released criminals could leave the country for elsewhere in Europe, where German police would no longer be able to shadow them.

Bernhard Witthaut, head of the GdP said the idea of using electronic tags as suggested by several federal states was an instrument rather than a solution.

“They do not prevent a single crime,” he said, suggesting that the monitoring centre where signals from the tags are overseen, do not have information about who is attached to the tags. He said the data can only be given to the police after a crime has been committed.

DPA/DAPD/The Local/hc