The National Union of Miners (NUM) called today for tighter health and safety regulations in the mining industry following the tragic death of four workers at a Swansea Valley mine.
The union said that ultimately the sector should be brought back into public ownership to ensure "no safety corners are cut to make profits."
The Wales Office and the Health and Safety Executive (HSE) have launched an investigation into the flooding at Gleision drift mine at Cilybebyll.
Mining expert Dr Eric Wade of the Open University called for a review of safety regulations, adding that the mine should have been drained beforehand.
The Mining Act 1978 says a "thorough examination" must be carried out before pit work can begin near flooded areas.
The HSE has promised lessons will be learned following the incident on Thursday, which led to the death of David Powell, Garry Jenkins, Phillip Hill, and Charles Breslin.
Local ex-miner Dai Thomas said at the weekend: "There was no such thing as health and safety for these boys. It is not viable to take coal out of these small mines without cutting corners."
National Union of Miners north-east general secretary David Hopper today called for a thorough investigation and for anyone found responsible for the deaths to be taken to task.
"Safety costs money and small-scale private operations such as this one is geared towards cutting corners to enhance profits," Mr Hopper said.
"These mines are no longer under the strictest of regulations, as they used to be when the industry was in public hands. Any investigation should recommend a tightening up of regulations across the industry."
Communist Party of Britain general secretary Rob Griffiths added: "What is left of the heavily subsidised private coal industry in Britain should be taken back into public ownership without delay."