Financial irregularities have prompted an investigation by anti-corruption authorities in Croatia.
Authorities reportedly believe long-term Dinamo president Zdravko Mamic ended up in possession of 7 million of the 21 million euros paid for the midfielder by Spurs in July 2008.
The report quotes the Madrid star as saying: "I was extraordinarily happy to go to the new club, and the best league in the world, and I had unlimited confidence in Zdravko Mamic… I did as they instructed me."
Modric rose to prominence at White Hart Lane – appearing 127 times between 2008 and 2012 – before Real Madrid came calling and prised him away for a deal worth around £30 million, according to BBC Sport.
The diminutive Croatian struggled initially and has had trouble with injuries but has proven himself on the biggest stage and controversy over previous transfers isn’t an ideal turn of events at this stage in his career.
For now, though, he must endeavour to keep his focus locked on the present, with Real having dropped two more points in La Liga over the weekend to now sit two adrift of table-topping Villarreal and one behind arch-rivals Barcelona.