The Government has ruled out nationalising the steel industry to tackle the threat of thousands of job losses after the Prime Minister admitted there were no guarantees of resolving the current crisis.
David Cameron chaired a brief meeting of ministers in Downing Street to discuss the shock decision by Indian conglomerate Tata to sell its UK assets, including the giant steelworks at Port Talbot in South Wales.
The leader of the Community union said he was "underwhelmed" by the Government's response, accusing ministers of not doing enough to lobby Tata before it made its decision.
A Labour petition calling for Parliament to be recalled has passed the 100,000 mark in just one day, with a new signature every second.
Business Secretary Sajid Javid was not at the meeting as he was travelling back from Australia after cutting short a business trip because of the unfolding crisis.
Workers at Port Talbot had been told Mr Javid was visiting the plant on Thursday but he will not be arriving back in the UK until late in the afternoon.
Mr Cameron said the Government was "doing everything it can" to resolve the steel crisis but nationalisation was not the right answer.
The situation in Port Talbot was of "deep concern" and there were "no guarantees of success", the Prime Minister said.
Mr Cameron defended the way the crisis had been handled, insisting the intervention had stopped an outright closure.
He said: "The situation at Port Talbot is of deep concern. I know how important those jobs are.
"Those jobs are vital to workers' families, vital to those communities and the Government will do everything it can working with the company to try and secure the future of steelmaking in Port Talbot and across our country, it's a vital industry."
Mr Cameron said energy costs in the industry had been cut and the Government had helped to make sure there were penalties for steel dumping.
"We are not ruling anything out. I don't believe nationalisation is the right answer."
About half of all British steel goes to other European Union countries, the Prime Minister said.
He added: "We need to be in there making sure the markets are open. If we were on the outside, we might well find that it was our steel that was having those tariffs and those taxes put upon it."
Roy Rickhuss, leader of the Community union, who met Tata officials ahead of the firm's board meeting earlier this week, said: "I have just returned from Mumbai where I have been with steelworkers meeting Tata, to hear an underwhelming statement from the Prime Minister.
"I am disappointed that the Government still has no plan for the industry but instead seems to be adding to the confusion and mixed messages that have been the state of play for the last 36 hours.
"The Prime Minister had the gall to state that his intervention with Tata was responsible for securing a 'sales process' but the sad truth is that Business Department ministers didn't take the opportunity to join us in Mumbai and the Government was nowhere to be seen.
"Now, thousands of steelworkers are faced with an uncertain future as their workplaces are put up for sale.
"This is not the third day of a steel crisis - we have been dealing with the consequences of the current global steel market for months, if not years. It is astonishing that the Government was so unprepared for Tata's announcement.
"Despite the Prime Minister desperately trying to get a grip of the situation, his Government's mixed messages continue - saying they will do all they can but still being unclear on the potential positive government intervention which may be essential to securing a future for steelmaking in the UK."
Labour leader Jeremy Corbyn tweeted that 100,000 people had signed the petition in less than one day, adding: "David Cameron must listen to the British people & recall Parliament."