Strike ballots are to be held again at four train companies where workers recently voted in favour but the legal threshold was narrowly missed.
Voting starts on July 28 and will end on August 25.
The original ballot of members saw the legal threshold for strike action, 40% of the entire electorate, missed by fine margins and in one case by just a single vote, said the union.
TSSA general secretary, Manuel Cortes, said: “We’ve had a strong set of ballot results for strike action across the rail companies our union represents and that reflects the strength of feeling about the government-created crisis on our railways.
“In a handful of companies, members voted overwhelmingly in favour of being able to take strike action but the numbers taking part fell just below the required artificial Tory threshold, often by tiny margins.
“That is a democratic deficit which cannot be allowed to stand.
“I’m extremely confident we will see a significant uptick in participation which takes us over the deliberately obstructive threshold.”