The Bluebirds’ Malaysian investor Vincent Tan is ready to pay Langston £9m up front, plus three payments of £2m during seasons when the club are playing Premier League football.
City chief executive Alan Whiteley said the written offer was sent to Sam Hammam, Langston’s representative, three weeks ago – with club officials now waiting for a reply.
Hammam is keen for Tan, who has already invested £40m-plus in the club and is preparing to take that sum past the £100m mark, to turn his loans into shares and make the club effectively debt free.
Mr Whitley said: “That was the latest condition, but that is irrelevant to Sam Hammam. It’s not for him to dictate.
“Vincent Tan owns the football club and whether the money is debt or equity in reality makes very little difference.
“Cosmetically, I would rather see it in equity because it makes the balance sheet stronger and it is our aim to improve the balance sheet.
“As and when the Langston issue is cleared up, the next thing to look at is how we then start strengthening the balance sheet by completing some of those conversions.
“If Sam Hammam wants the club to be debt free why doesn’t he turn the loan notes into equity? We could look at that if he wants to.
“It makes sense for everybody to get this sorted out as soon as possible.”
Multi-millionaire Tan, who owns the rights to McDonald’s and Starbucks in Malaysia, plus a string of betting companies, invested in Cardiff City at a time when the club was facing major financial difficulties.
“Vincent Tan rescued this club two and a bit years ago at a time when it was two weeks away from being wound up by the Inland Revenue,” Mr Whitley said.
“There was nobody else on the scene willing to invest and we had to find between £2m and £3m just to pay off the revenue and historical creditors who were banging the door down and getting more irate because they weren’t being paid.
“These were people who had done work on the stadium, including fitting out the stadium.
“The £6m our Malaysian investors put in at that stage literally went to pay off debts.
“Funding over the next two years enabled us to address some of the working capital problems and get the club back on a level footing, including assembling a better squad capable of challenging for promotion.
“The only conclusion which can be reached is that the club is getting more professional year by year and we are constantly striving to improve the experience for supporters.
“Regardless of the controversy over rebranding, anybody looking at this objectively would say the club is far more professional now than at any stage in its history. A large part of that is because there is money to do things a lot of people wanted to do but didn’t have the backing to get on with them.”
On the latest £15m offer, Mr Whiteley said: “We have put the offer in writing to ensure there is no misunderstanding or miscommunication. It was made three or so weeks ago.
“We have left it firmly with Langston for them to come back to us.
“We have put a variety of offers in place and for a variety of reasons they have been rejected. We have not yet had an answer on his latest offer.”