Entrepreneur Sanjeev Gupta, chief executive of Liberty Steel, acquired the aluminium plant and two adjacent hydro power plants in 2016.
The Scottish Government has contributed up to half a billion pounds in guaranteed loans for the smelter and the hydro power plants, worth a total of £586m.
And the deal has come under fire after the Sunday Times revealed Mr Gupta’s firm contributed £5 to the deal, according to documents filed at Company House.
Mr Gupta’s family empire, GFG Alliance, is the subject of alleged fraud and money laundering investigations.
The company have denied any wrongdoing.
Now the Scottish Liberal Democrats economy spokesperson, Willie Rennie, is urging the Scottish Government to “end the secrecy” and announce the details of the deal.
It comes as the UK Government withdrew guarantees on £400m of loans Greensill Capital made to the tycoon’s companies.
The Scottish Government has been urged to follow suit and protect hundreds of million pounds of public finances.
Mr Rennie said: “The SNP Government has been gullible once again.
“Two thousand jobs were promised by Gupta which have not been delivered.
“We knew that the Scottish Government’s industrial intervention strategy was a disaster, but this takes it to a new level.
“We need a statement from ministers to finally properly explain this deal, the financial exposure for the Government and its detailed plan to recover the position and limit the exposure for the taxpayer.”
Jamie Halcro Johnson, Scottish Conservative business spokesperson, told the Sunday Times it was “staggering” the Government was prepared to risk more than half a billion pounds.
It comes as The Scotsman reported that fresh disclosures have raised questions about the ability of GFG Alliance to meet conditions required to abide by the Government’s £586m Lochaber guarantee.
Minutes of a guarantee management meeting, held with advisers from Deloitte, PR firm Teneo, and members of the government and GFG Alliance, raise questions about the ability of GFG to pay for the billet plant’s construction, which may have an increased budget.