Welsh star Gareth Bale joined Real Madrid in 2013 for a world record fee in excess of 100 million euros ($109 million, £77 million), a leaked report reveals.

Whistleblowing website Football Leaks posted a copy of the agreement between Madrid and Tottenham Hotspur online on Wednesday.

The deal allowed Madrid the option of paying 91,589,842 euros in one lump sum within 15 days of the transfer, or 99,743,542 euros in four instalments over three years.

Madrid also agreed to pay a solidarity fee of 1,015,875 euros and forego any outstanding payments on the transfer of Dutch midfielder Rafael Van der Vaart to Tottenham from Madrid in 2013.

Numerous Spanish media outlets reported Madrid had taken up the four instalment option.

Real Madrid refused to comment when contacted by AFP on Thursday.

However, Bale's agent Jonathan Barnett called for an investigation into how the documents came to be leaked.

"There should be an inquiry and an independent investigation because it’s outrageous," he told The Telegraph.

"There also needs to be an apology from the Football Association to the clubs and the player.

"I think it’s disgraceful that people can get hold of this sort of stuff. It shows complete disregard for both clubs and the player."

Real have long maintained Bale only cost 91 million euros.

Indeed another provision of the contract states Madrid would cite that figure to the media, whilst Tottenham wouldn't release any statement regarding the transfer fee.

In exchange, Madrid agreed to ensure Bale wouldn't make any "negative or derogatory comments" regarding Tottenham and their chairman Daniel Levy.

Madrid were reluctant to announce a world record fee to appease Bale's teammate and three-time World Player of the Year Cristiano Ronaldo, whose move from Manchester United to Madrid for 94 million euros in 2009 was the previous record.

Bale has consistently been linked with a move back to England with United among those rumoured to be interested.

However, according to the agreement, Tottenham have a right of first refusal should Madrid sell Bale back to the Premier League before 2019.

Bale enjoyed a stellar first season in Madrid, scoring in the finals as Real won the Champions League and Copa del Rey against rivals Atletico Madrid and Barcelona respectively.

However, after a poor second season, the 26-year-old has been hampered by injuries so far this year.

He is expected to be out for the next three weeks after picking up his fifth calf muscle injury since joining Madrid in Sunday's 5-1 win over Sporting Gijon.

Yet, Madrid sports daily Marca reported on Thursday that the club are set to offer Bale a new contract on improved terms until 2021.