Anonymous hackers have posted emails allegedly proving the Mexican government is modifying a climate change bill to protect the coal mining industry from taxation.

The group targeted the Mexican Mining Chamber, also known as "Camimex", stealing and posting online more than 700 Megabytes of data.

"You only took out our minerals, exploiting our miner brothers," reads a statement on Pastebin.

The collective claims the recent opening of gold and silver mines in San Luis Potosi by Canadian company First Majestic Silver will put the indigenous population at risk and destroy "sacred sites and devastate the environmental resources of the zone".

In an email exchange dated 26 January 2012, members of the Camimex claim that Mexican MPs are monitoring the Climate Change Act (Ley de Cambio Climático) to ensure "it does not affect growth".

The bill - which was approved by the upper house or Senate in December with a vast majority and will now be debated by the Chamber of Deputies - aims to create a domestic gas trading system able to cap and cut carbon emissions.

But federal representatives of the north-eastern top-mining state of Coahuila, where 95 percent of Mexico's coal reserves are found, will allegedly promote "modifications" to the law to help mining company based there.

"The intention is to avoid imposing taxes that can constitute a disadvantage to productive sectors such as coal mining," read one email.

According to it, the governor of Coahuila Ruben Moreira Valdez is aware of the strategy, having stated during a press conference that jobs in the coal mining sector "must be protected".

In its statement, Anonymous denounced the mining companies and unions, suggesting they are working together "to steal our minerals with a value over $200,000,000 and forcing our miners to work in extreme danger conditions".