Union leaders are calling on David Cameron to take personal charge of talks to prevent the closure of Tata Steel’s Port Talbot plant.
They have accused Business Secretary Sajid Javid of “taking his eye off the ball” and say the PM needs “to get a grip” of the negotiations.
It comes ahead of emergency talks in London between unions and representatives of at risk Tata plants.
The government has said it will offer financial support to help find a buyer.
Tycoon Sanjeev Gupta, founder of commodities firm Liberty House, has had initial talks over a potential purchase of the south Wales plant.
Liberty House said the talks had been “positive” and ministers were “keen to find solutions”. Mr Gupta will return to London on Monday evening to continue the negotiations.
Mr Javid is to meet Tata’s chief finance officer later amid reports Investment firm Greybull has been in talks with the company regarding a buy-out of its Scunthorpe operation.
Marc and Nathaniel Meyohas, the brothers behind the firm, are considering a £400m investment in the struggling Lincolnshire plant, potentially saving about 9,000 jobs.
However, it is understood German group ThyssenKrupp have signalled they are not interested in buying Tata Steel’s UK businesses.
Meanwhile, Wales’ First Minister Carwyn Jones faces questions from assembly members over the steel crisis later in a hastily reconvened meeting. Mr Jones is expected to hold talks with Mr Cameron in Downing Street on Tuesday.
Tata Steel announced last week it was selling its loss-making UK businesses and would close its plant at Port Talbot unless a buyer is found.
The company directly employs 15,000 workers in the UK and supports thousands of others, across plants in Port Talbot, Rotherham, Corby and Shotton.
It is understood Liberty House would be unlikely to buy Port Talbot’s blast furnace and is primarily interested in the company’s rolling mills and other steel processing plants, said BBC assistant political editor Norman Smith.
A source involved with the talks said the company and other potential buyers would regard taking on Tata’s pension liabilities as “too big an ask”.
There are around 140,000 steel workers eligible for pensions under the Tata scheme – also including the old British Steel pension scheme.
Mr Javid, under pressure over his handling of the crisis, signalled on Sunday that ministers were working on plans to take on some of the pension liabilities and to reduce energy costs to make a purchase more attractive to investors.
But Norman Smith said there was concern that a government move to cover workers’ pensions could flout EU state aid rules.
Shop stewards from steelworks across the country are meeting in London shortly to discuss the steel industry crisis as efforts continue to save thousands of jobs at risk.
The unions say they wrote to Mr Cameron last week seeking a meeting and have not received a reply – but Downing Street said no correspondence had been received.
Unite assistant general secretary Tony Burke said: “We want the prime minister to step in… last week was an absolute disaster. It’s important the prime minister now meets with the unions to look at all the options.”
He told BBC News the unions wanted to “know what’s going on”, saying there were “more questions than answers” over the future of Tata’s UK business.
Roy Rickhuss, leader of the Community union, added: “By now, no-one underestimates the scale of the challenge we face. We have an entire industry to save and not a lot of time to save it.
“We must also ensure that we hold Tata to a commitment to be a responsible seller and honour its moral and social duties to UK steel communities.”
Ahead of a visit to Rotherham steelworks, Business Minister Anna Soubry said the government wanted to find a buyer who would purchase Tata’s UK operations “as a whole”.
“We need to make sure we get the right deal, obviously that deal is for Tata to decide because they’re a private company, but that we do everything we can to make it happen,” she told BBC Radio Sheffield.
Tata Steel has said there is “no fixed timeline” for the sale process but stressed that urgency is needed to avoid “a long period of uncertainty” for employees and customers.
Labour says the government should be prepared to take the Port Talbot plant – which Tata says is losing £1m a day – into public ownership to safeguard its future until a buyer can be found.
The Welsh Assembly has been recalled from its Easter recess to discuss the crisis, amid calls from its members for the UK and Welsh governments to work together to reduce business rates.
Welsh Economy Minister Edwina Hart, who is chairing a steel task force, said Cardiff was willing to look at this, but stressed UK-wide rules limited how much rates could be varied.
It was up to the UK government to take the lead on “fighting for steel” by stepping in with cash, including investment into plants and machinery, she added.