LISBON (Reuters) - A former owner of Portugal's flag carrier TAP, David Neeleman, denied on Friday making a deal in 2015 to overpay for Airbus planes after prosecutors said last month they were investigating the complex leasing deal, as well as suggestions he had bought TAP shares with company money.

"It is also completely absurd to say that TAP shares were bought with Airbus funds or with TAP's future cash flows," he wrote, adding that TAP exclusively used the $226 million from Airbus in ancillary benefits to pay salaries and for its cash needs.

Sources told Reuters last month investigators were looking into Airbus' possible illegal financing of the TAP acquisition, in a new probe into the plane maker's business dealings following a record $4 billion corruption settlement with French, British and U.S. authorities in 2020.

The 2015 deal under investigation dates back to when TAP, now again fully state-owned, had just been privatised, passing control to the Atlantic Gateway venture between Neeleman and Portuguese entrepreneur Humberto Pedrosa.

Neeleman said it "was also not true" that TAP acquired the NEO planes above market prices, citing independent assessments carried out at the time, and argued that the airline simply could not afford the larger, less efficient A350s and would have gone bankrupt without the new deal.

He said Atlantic Gateway had also injected its own funds into TAP and arranged a 90 million euro ($96.04 million) loan from Azul, the Brazilian airline that Neeleman founded, "on very favorable terms for TAP", saving TAP from immediate insolvency.

Portugal in 2020 bought Neeleman's stake in TAP, which is under a 3.2 billion euro Brussels-approved bailout. The government is considering an outright or partial sale of the airline, with Lufthansa, Air France-KLM and British Airways owner IAG expected as potential buyers.

($1 = 0.9371 euros)

(Reporting by Andrei Khalip and Patricia Rua; Editing by Josie Kao)