The multi-millionaires who bought British Steel for £1 in 2016 and are now seeking financial aid from the government are charging £20m a year in fees and interest from the company.

Marc Meyohas and Daniel Goldstein are in talks with British Steel’s lenders over a £75m rescue package that is understood to be at risk of falling apart unless the government contributes.

The company, which owns the Scunthorpe steelworks, claims that without the new funding it could collapse, putting 4,500 jobs at risk.

Meyohas, the son of a wealthy French corporate lawyer, and Goldstein have charged £33.8m in interest on loans their private equity fund Greybull Capital made to British Steel at a rate of 9.6%, according to filings at Companies House.

The money was loaned via a Greybull business registered in the tax haven of Jersey. The firm said the offshore structure was not designed to avoid tax.

The pair, who run their investment fund from offices above a Jimmy Choo store on Sloane Street, around the corner from Harrods in central London, have also charged British Steel £6m in “management fees” since they took control of the Scunthorpe works in 2016.

As part of Greybull’s rescue of the plant from Tata Steel, staff took a pay cut in the first year and about one in 10 were laid off in an efficiency drive.

A spokeswoman for Greybull said the £250,000-a-month management fees charged to British Steel were for “extensive” services “charged at a significant discount to normal market rates”.

The spokeswoman said Greybull was charging such a high rate of interest on its loan because of British Steel’s low credit rating. She added that British Steel had yet to pay the interest bill to its owners.

“Most importantly no interest has been paid by British Steel to Greybull since our acquisition of the business in 2016,” she said. “All interest has been accrued and not paid. This has been done in order to support British Steel’s financial position through its turnaround.”

The attempt to raise £75m in funding comes less than a fortnight after the government provided British Steel with an emergency £120m loan to cover a bill from the EU for its carbon dioxide emissions.

Quick guide What went wrong at British Steel? Show Hide What plans does Jingye have for British Steel? Jingye's financial profile is relatively opaque, but the company is expected to pledge investment worth £1bn over the next decade. A person briefed on Jingye's thinking said the company wanted to preserve as many jobs as possible, but could not say how many of the company's 4,000 workers would keep their jobs. British Steel accounts for a third of UK production, so is seen as a key national asset in many quarters.

What went wrong at British Steel? When Greybull Capital bought British Steel in 2016 it promised great things. The private equity firm pledged to invest £400m and within months it was boasting of a return to profit and a bright future ahead. Three years later it collapsed. In a letter to staff, the British Steel chief executive blamed weak market demand, high raw material prices, the weakness of sterling and uncertainty over the outcome of Brexit discussions. Who is Jingye? Jingye emerged as the most likely owner after talks with Ataer, a division of the Turkish military pension fund Oyak, fell through in October. Founded in 1988 by a former Communist party official, Li Ganpo, the Chinese conglomerate has hotel and retail interests. However, steelmaking, which it started doing in the early 1990s, is now its primary focus: its Chinese mills produce about 15m tonnes of steel a year, exporting to 80 countries. How much is Brexit to blame? It is not the only factor in the crisis, but it is important and will remain crucial even if Jingye buys British Steel. Steel contracts are typically agreed well in advance of the product being delivered. As things stand, the UK is due to leave the EU on 31 January after another delay, and the terms of that separation are yet to be agreed, meaning British Steel’s overseas customers do not know what tariffs will apply to steel they buy from the company. Sources close to the company said orders from customers in the EU and further afield had dried up as a result. Is the whole UK steel industry in trouble? The UK steel industry has been in decline for some time because of a variety of factors such as overcapacity in EU steelmaking and Chinese state-subsidised firms flooding the global market with cheap product. An industry that employed 323,000 people in 1971 now employs less than a tenth of that, at 31,900. The closure of the Redcar steelworks in 2015 was a significant blow to the sector and left the UK with only two blast furnace steelworks: Scunthorpe and the Tata Steel-owned Port Talbot in south Wales.

The prime minister said on Wednesday that she could not comment on “the future of Greybull Capital-owned British Steel” but conceded that it was a “worrying time” for employees and their families.

“Last month the government did enter into a commercial agreement with British Steel relating to their obligations under the EU emissions trading scheme which has provided support to that company,” she added.

Greybull says that it is “passionate about making companies successful”. However, as well as British Steel, the firm backed the attempted rescues of Monarch Airlines; retailers Comet Group and My Local; and Rileys snooker hall business. All of those businesses collapsed, putting several thousand people out of work.

While almost 1,900 Monarch workers were made redundant (and more than 100,000 holidaymakers left stranded overseas) when Monarch collapsed in 2017, Greybull was the top creditor, collecting almost £60m from the administration. Greybull also collected part of a £50m payment as one of the main creditors in the collapse of Comet, in which 7,000 people lost their jobs.

Meyohas has said he decided to set up Greybull in the wake of the financial crisis, when traditional banks withdrew lending, as he spotted an opportunity to charge higher fees.

“We felt there was going to be opportunities for providing capital to companies that wanted to develop themselves – either grow or restructure – particularly after the Lehman crisis, when a lot of banks and capital providers decided to shut up shop,” he told Bloomberg.

The Scunthorpe steelworks is one of the last two left in Britain along with Port Talbot in south Wales, after the Redcar facility on Teesside closed in 2015. It supplies steel for customers including Network Rail and supports 22,000 jobs in its supply chain, on top of 4,500 direct employees.