John McDonnell MP's Private Member's Bill, which would have stopped courts ruling out strike ballots on small technicalities, was defeated in Parliament on 22 October.
Ed Miliband, when standing for Labour leader, volunteered in a statement to the unions that he would back moves to stop judges invalidating strike ballots on the basis of minor errors.
But Ed Miliband's front bench refused to back McDonnell's Bill, and would not mobilise enough Labour MPs to attend the House of Commons to get the Bill on to its next stage.
Labour shadow minister Nia Griffith refused to support Mr McDonnell's Bill, even though she acknowledged that the present situation was "unsatisfactory," with employers seeking legal loopholes.
Ms Griffith said: "I have to make it clear that although the opposition recognises the need to restore the original intention of the 1992 Act, we cannot today endorse the particular legal mechanism contained in this Bill."
A total of 89 Labour MPs turned up to support the Bill, including two who acted as tellers in a procedural vote of 87 to 27.
But the Bill fell into a parliamentary black hole because at least 100 supporters were required to force a vote on the second reading.