Thousands of jobs have been put at risk by the news, including at the Port Talbot facility which is Britain's largest steelworks.
General secretary for union Unite, Len McCluskey, said the growing calls for renationalisation "cannot be ignored" by the government.
"We are now in the grip of an industrial crisis. Decisions taken in the days to come will determine not just the futures of 19,000 workers and their families, across 14 sites, but the very success of this government's own economic programme," he said.
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"This is the time for the government to say categorically, without hesitation, that these assets will be taken into safe-keeping by the nation because without them our economy will not flourish. We are already seeing jobs going in the supply chain because of the uncertainty over Tata's future – our fear is this will snowball if insecurity is allowed to swirl around our steel sector.
"The unity of voices – from business to government – to say that temporary nationalisation is the way forward must not be ignored. This helped save the Scottish plants. It has ensured that the Ilva plant in Italy survived – it must be deployed for the rest of the Tata operation."
Mr McCluskey added: "Such is the scale of the matters before us that the Prime Minister must assume charge of the strategy from here on in. This will send the clear signal to the workforce, the industry and potential buyers that the government is serious and driven about saving this foundation industry."
(LM)
