Boris Johnson has said he is “very hopeful” a solution can be found to save Liberty Steel as the firm’s owner insisted none of its plants would be shut “under my watch”.

Sanjeev Gupta has been urgently seeking to refinance its operations following the collapse of its main financial backer, Greensill Capital, threatening an estimated 5,000 jobs in the UK.

The Government has previously rejected an appeal by Liberty’s parent company, GFG Alliance, for a £170 million bailout amid concerns its “opaque” structures meant the funds could disappear into its international operations.

However, the Prime Minister said Business Secretary Kwasi Kwarteng remained in “daily contact” with the owners.

“I think British steel is a very important national asset. I think the fact that we make steel in this country is of strategic long-term importance,” he told reporters during a visit to Middlesbrough.

“We need a strong steel industry. I am very hopeful that we will get a solution.

“It would be crazy if we were not to use this post-Brexit moment to use the flexibility we have to buy British steel. So that’s what we want to do.”

Earlier, Mr Gupta said he was continuing efforts to find new sources of finance as he disclosed that they owed “many billions” to Greensill.

He insisted however that its overall global operations remained profitable and that they had had a “huge amount of interest” from financiers who were willing to back them.

“Of course, given the situation, this sort of thing takes time and hence we need to find short-term solutions. But we’re not waiting for anybody. We’ve taken matters into our own hands,” Mr Gupta told BBC Radio 4’s Today programme.

“Our overall global operations are profitable, we have refinancing offers, we will refinance and we will support our UK business also. None of my steel plants under my watch will be shut down.”

He accepted that “the UK has been a tough journey” and “labour of love”, but added that he was “committed to my UK steel plants”.

“I believe in them, they have a great future. We’ve saved thousands of jobs here. We’ve shown that economically those businesses can work,” he said.

Mr Gupta said there had been “positive discussions” with the administrator for Greensill.

They had “committed facilities” from the financier for three years and that “according to us, these debts are not due”.

He added: “It makes no sense for them or any of the creditors to destroy jobs but, more importantly, to destroy value, because that is the value which will give them the recovery.

“I’m very confident that we will find short-term solutions through our own efforts and will find long-term solutions through refinancing.”

Greensill filed for insolvency earlier this month after failing to secure support through the Government’s Covid Corporate Financing Facility.

Ministers have since been facing questions over lobbying by David Cameron on Greensill’s behalf – including reportedly sending text messages to the Chancellor, Rishi Sunak.

Asked if the former prime minister did any lobbying work for him, Mr Gupta replied: “I have not had any interactions with him.”