Emiliano Sala was "abandoned" by Cardiff City and had to arrange his own travel in a £15m transfer from Nantes, says ex-football agent Willie McKay.
McKay's son Mark was Nantes' acting agent in the deal for the footballer, who died in a plane crash last month.
Willie McKay arranged the flight that crashed in the English Channel, killing Sala, 28, and pilot David Ibbotson.
Cardiff say they "strongly reject" the claim they neglected to provide Sala with travel arrangements.
"He was abandoned in a hotel more or less to do his travel arrangements himself," Willie McKay said.
But in a statement, Cardiff said: "Our club was in the process of organising a commercial flight for Mr Sala until this offer was declined owing to separate arrangements being made - the planning and specifics of which Cardiff was not privy to.
"Cardiff has serious concerns over the potential unlawfulness of the journey following information that has been released. Clearly more answers as to the details surrounding this terrible tragedy are required."
Willie McKay is not a registered agent but when asked why he was involved in the Sala deal, he replied: "I was helping my son."
The body of Argentine Sala - the Bluebirds' record signing - was found in the wreckage of the Piper Malibu N264DB, which was found on the seabed 13 days after it vanished over the English Channel near Guernsey. Ibbotson's body has not been found.
"I wish I had never gone to watch the guy play," said Mark McKay. "I wish I had never known anything about it in the first place."
Speaking to the BBC, the McKays say they have been made "scapegoats" but believe investigations will show the crash was a result of "pilot error".
In a wide-ranging interview, the father and son also say they:
- Learned Sala was missing through a phone call from Cardiff boss Neil Warnock
- Were paying the entire sum of Sala's travel
- Will not chase Nantes for the money they are owed for brokering the deal
- The crash has made Mark McKay question his future in the industry
'Cardiff let themselves down'
Having signed for Cardiff, Sala flew back to Nantes on 19 January to say goodbye to his former team-mates before planning to return to the Welsh capital on 21 January.
Willie McKay said the disappearance of Sala's plane was first brought to his attention when he received a phone call from Warnock.
"Neil had called Mark and he told him to phone me," Willie McKay said.
"He told me the player liaison officer was waiting for Emi to come off the plane and it hadn't arrived. They feared the worst."
- Cardiff transfer payment investigated by Fifa
- Text messages over flight revealed
- Sala profile: Born in Argentina, forged in France
Willie McKay arranged Sala's flight to Cardiff through David Henderson - an experienced pilot who had flown him and many of his players "all over Europe on countless occasions". McKay did not own the plane and says he did not know who Henderson was going to ask to fly the plane.
"Nobody in Cardiff seemed to be doing anything. It was a bit embarrassing for Cardiff," Willie McKay said. "They buy a player for 17m euros and then leave him in a hotel by himself to go on the computer and look for a flight - I think Cardiff let themselves down badly.
"The way they've acted so far, they've been a disgrace."
In January, Cardiff told the BBC the club does not have a private jet for players to use and therefore they could not be expected to have arranged his travel to and from Nantes.
They added that "the relevant authorities must be allowed to determine the facts surrounding this tragedy". They are currently investigating the details of the flight.
'We were paying for the flight'
In recent weeks, questions have arisen regarding the pilot's licence held by Ibbotson, and in an interim report this week, air accident investigators said he did not have a licence for commercial flights and could only fly passengers in the EU on a cost-sharing basis.
However, in what could cast fresh doubt over the legality of the flight, Willie McKay said it was not a cost-sharing agreement as "Emi wasn't paying anything" and that he was going to pay "whatever Dave [Henderson] was going to charge".
"When you phone for a taxi you don't ask him if he has a driving licence," he said. "I was just thinking about getting the boy home which he wanted and we were happy with what we did.
"I've been told on good authority he was a very good pilot so for people to vilify the pilot after a man's death is a disgrace. I don't hold anyone responsible because it's just a tragic accident."
Willie McKay claims Nantes owe his son £1.5m for brokering the deal but said "they won't be chasing Nantes for the moment".
"This is not about money, it's about two lives that have been lost," he said. "You're prepared to lose that £1.5m given the circumstances.
"I've got three great kids and a wife who have been very strong through this - if others want to argue about money let them, but we won't be arguing about money."
'We've been through hell'
Fifa is investigating the transfer payment for Sala after Nantes made a claim against Cardiff.
The Welsh side were due to make the first of three instalments on 20 February, but they agreed with French Ligue 1 side Nantes to extend the deadline by a week.
Nantes wrote to Cardiff on 5 February requesting the first instalment, which Cardiff were due to pay the first of on Wednesday.
Cardiff said they were withholding payment until crash investigations were complete and they were satisfied about "anomalies" around the deal.
"I don't care, to tell the truth - I really don't care because what we've been through is total hell," Willie McKay said.
Willie McKay says the weeks since the crash have been "very, very difficult" for himself and his family, adding he feels "great grief" for the families of the deceased men.
But his son said he "doesn't see" how they would have ever done things differently and hopes "everyone can stick together".
Mark McKay admitted the incident had made him question his future as a football agent but added it was not the right time to think about it.
"You don't make decisions when you're in a place like this," he said.
"At the end of the day I don't want to sit here and be a victim because I'm not and that's a fact. But its been tough and its been tough for people around me."