The NACODS union says thousands of former pit workers may have to prove their condition by walking faster and faster to the point of exhaustion.

The union has objected to the government, which says no final decision has been made.

Thousands of miners face examination to determine their right to compensation following a High Court ruling in January which established their right to claim.

Chest diseases such as bronchitis; emphysema; chronic obstructive airways disease and asthma are particularly common among miners.

Shuttle test

NACODS claims the Department of Trade and Industry wants the men to undergo a "shuttle test" which involves a lung function test before having to walk around two cones placed 9.5m apart.

The men have to speed up their walking time to a bleeping sound that gets faster and faster until they are too exhausted to carry on. They are then given a further lung function test.

Miners leader Bleddyn Hancock said: "After a ten year legal battle I expected that we should now be settling these claims, but the government seems determined to drag them out while decent men and widows die.

"We have proposed that all these men should attend NHS hospitals to be assessed by chest consultants, but the DTI want to use private companies to use this test that our medical experts have told us will be inconvenient to the majority, distressful to many and fatal to a few."

Mr Hancock said many old miners suffered from arthritis or rheumatism and some had heart conditions.

A DTI spokesman said: "There is no way the government is going to force people to take a test that is going to cause them injury."