The fight against crime needs to be beefed up with better detective work, Police Minister Nathi Mthethwa said on Tuesday.

"We are slack when it comes to the capacity of detectives... you have a low conviction rate if you don't have thorough detection work," he told the central executive committee of the Congress of South African Trade Unions (Cosatu) in Johannesburg.

"We need to strengthen that area," said Mthethwa.

He was briefing Cosatu on how the government planned to step up the fight against crime, saying strategic partnerships and community involvement were key elements.

An important "pillar" in the government's crime stopping campaign was to send out the message that it was fighting crime "toughly and smartly".

This was "so that we deal with the perception that this government is soft on criminals", said Mthethwa.

The justice department was in the process of reviewing the policy on repeat offenders, who should be dealt with more harshly, said Mthethwa.

He said the Hawks had drawn up a list of the 50 most wanted and dangerous criminals in the country and claimed that most of them had already been arrested.

"The last time I checked, about 46 were already nabbed," said the minister.

The Hawks were also strengthening the "fight against corruption, including cyber crimes," he said.

Journalists, who were invited to the event, were asked to leave the room before Mthethwa finished his speech.

In his introduction, Mthethwa jokingly referred to "threats" that had been made between Cosatu and the government recently, saying: "We need peaceful threats".

Before him, Labour Minister Mildred Oliphant addressed the meeting, but journalists were also asked to leave after she made her introductory remarks, which included that the government and Cosatu should work together.

She said that she hoped the government would come up with proposals on how to deal with labour brokers.

"We will report to you," said Oliphant.

Also, Cosatu needed to take part when the government drafted legislation dealing with workers.

"That participation hasn't happened... whatever legislation the government is tabling, you must participate as workers," said Oliphant.

Minister in the Presidency, Collins Chabane, was scheduled to address the meeting but this was cancelled at the last minute.