A committee of MPs blamed the company for its own collapse
Tube workers at the failed private firm Metronet have backed strike action in a row over staff transfers and pensions.
The Rail Maritime and Transport (RMT) union said 751 of its members voted for industrial action, with 171 against.
It fears members will be forced to join other employers when Metronet contracts are transferred to Transport for London (TfL) and suffer worse pension deals.
A spokesman for TfL said the RMT has been assured that no staff will lose jobs, pensions or be transferred.
Metronet went into administration last July after an estimated £2bn overspend.
Last month, the House of Commons Transport Committee said the company and it's shareholders were "primarily responsible" for its collapse.
"The transfer of these contracts is highly complex, but we need simple guarantees on the security of our members' jobs and their pensions," said RMT leader Bob Crow.
"It is one thing to be told that there are intentions, but intentions are not guarantees and we have already made it clear that it would be unthinkable for the transfer of Metronet back to the public sector to be used as a Trojan horse for a two-tier workforce."
A spokesman for TfL said: "Industrial action would be completely unnecessary and not achieve anything.
"The RMT have been given guarantees that no staff will lose jobs, pensions or be transferred as a result of Metronet's collapse. Indeed, the vast majority of Metronet employees already enjoy these benefits.
"We have an agreement with the trade unions on all these issues, hammered out during the previous dispute, that it was agreed would last through the period of administration.
"Metronet remains in administration. We urge the RMT to acknowledge their agreement and the assurances given."