Italy's most powerful trade union has pledged to campaign to expose black market practices and assert workers' rights in the clothing industry after a fatal fire at a Chinese-run garment factory in Tuscany, Italy early yesterday (1 December).

The Confederazione Generale Italiana del Lavoro (CGIL) hit out after seven people died when the blaze swept through an illegal dormitory in the roof space of the factory on the Macrolotto industrial estate near Prato. Four others were injured. Police and fire brigade investigations are continuing.

Prato has become a magnet for Chinese-run clothing plants manufacturing garments for international retailers. Many Chinese workers are not registered for work and live in the factories, which undercut Italian producers.

The CGIL claimed Prato probably has the largest concentration of illegal labour in Europe.

In a statement, the local executive of CGIL said: "This was a tragedy waiting to happen, a direct consequence of the serious living and working conditions people are forced into in extreme weakness and are unable to rebel against because they are at the margins of legality."

It continued: "The battle for working conditions is the first battle: this applies to all companies, of all nationalities, who operate in our country."

Italian-language media reported that the local police and Italy's Guardia di Finanza financial police joined immigration, social services and other authorities this morning to raid another Chinese-run garment factory in Prato, seizing production machinery and detaining workers whose employment status was irregular. The police also found a loft converted into a dormitory in the building.