Former miners and their families have been warned by a UK minister to ignore "parasite" agents trying to get them to register for compensation claims.
Don Touhig says the compensation agents are a 'con'
Wales Office Minister Don Touhig said so-called "claim farmers" who are acting within the law were "preying" on elderly people by cold calling them.
Mr Touhig, the Islwyn MP, says he has been contacted by many worried constituents.
The deadline for registration for claims for chest diseases suffered as a result of working underground is midnight on Tuesday - 31 March - and families of miners who have still to make claims are being urged to go directly to solicitors.
The compensation agents can make money by selling a miner's details to solicitors who then process the claim for them.
Some families have reported receiving multiple calls from the same company agents, even after they tell them they are not interested.
Peter Evans, a partner with the law firm Hugh James, is very concerned with the harassment some families have experienced, describing the aggressive sales tactics as "deplorable".
He said any miner or their relative who receives a call from an agent in this way should tell them in no uncertain terms to go away.
Mr Touhig told BBC Wales the claim handlers were "parasites" preying off elderly people trying to persuade them even if they had a claim made they could make another one.
"It's impossible - if you've been successful [with one claim], you can't make another one.
"I'm dealing with one now where one of my constituents has parted with £5,000 to a claims handling company and on the papers he signed, it said the company would pay all the legal and medical costs on behalf of the claimants.
"There are no costs for the claimant. They have all been met by the government.
Miners have until 31 March to register compensation claims
"Frankly, it's a con. I would urge anybody who's approached by these claims farmers - don't touch them with a bargepole.
"If you have a claim to make, get hold of a reputable solicitor and go through the proper process."
He added one solicitor had recently been contacted by a claims agent saying it had collected 10,000 claims.
Mr Touhig said it was impossible that the claims could all be registered in time for the deadline.
One miner from the Blackwood area said he had been bombarded by calls.
"Even when I tell them I have put in for a claim, they are still fairly persistent.
"They want to know how much we have claimed - in the end, I put the phone down."