Uefa, which is among the football bodies now calling for Mr Infantino to step down from Fifa, also paid for the woman to attend an MBA course at a business school that charged fees of about £45,000 a year as part of the deal.
The woman – whom The Telegraph has chosen not to name – was in an administrative position when their relationship began, but was subsequently promoted to a more lucrative managerial role, sources claim.
When she left, Mr Infantino allegedly used his connections to secure a new lucrative post for the woman, in a similar field.
He also secured her pay-off, diverting Uefa funds that could have been spent on grass-roots football, including in the UK.
Regulations tightened
On Friday night, a Uefa spokesman confirmed the pay-off and insisted that the organisation had since changed to become more modern.
He said: “We are aware of the allegations and can confirm a departure payment was made to the individual in question, coupled with the payment of fees for an MBA course at a local business school. The payment was in line with the regulations that existed for departing staff at the time.
“Such regulations have been tightened since 2016 and the current staff regulations – which apply to all Uefa employees at whatever level – reflect those found in a modern, high-profile organisation.”
Mr Infantino is said to have promoted his alleged lover, giving her a pay rise of 30 per cent and a salary of about 160,000 Swiss francs (£147,000).
Her rapid rise is said to have prompted questions among colleagues, and concerns that he could be abusing his powerful position to advance her.
At the time he was responsible for a football empire overseeing the sport in 53 countries with revenues of about £1.2bn.
Mr Infantino met his wife, Leena Al Ashqar, through football. She worked for the Lebanese Football Federation. They married in 2001 and have four daughters.
It is unclear whether Ms Al Ashqar was aware of the alleged relationship. However, matters are said to have come to a head when Mr Platini learned about it.