Brazil footballer Neymar has appeared before a judge to testify in an investigation into alleged irregularities regarding his transfer to Spanish giants Barcelona.

Neymar's father, who acts as his agent, was also going to be questioned by judge Jose de la Mata at the National Court in Madrid.

Current Barcelona president Josep Bartomeu and predecessor Sandro Rosell denied any wrongdoing when they testified on Monday.

The court is looking into a complaint made by a Brazilian investment group which claims it was financially harmed when Barcelona and Neymar allegedly withheld the real amount of the player's transfer fee from Brazilian club Santos in 2013.

Investment group DIS was entitled to 40% of Neymar's transfer from Santos, but claims it received a smaller compensation than it should have because part of the transfer fee was concealed.

Neymar, wearing jeans and a jacket, arrived with his father and other members of his staff. They made it to the court in central Madrid just before the scheduled time for their testimonies.

Santos's representatives were also in court on Monday and said the club was deceived by Barcelona and Neymar.

Representatives from Barcelona told the judge that all legal protocols and regulations were met in Neymar's transfer. Mr Rosell resigned in 2014 because of the allegations involving the Brazilian player's transfer.

Barcelona maintains that the deal cost the club 57.1 million euro (£43.25 million). Santos officially received a payment of 17.1 million euro (£12.95 million), with the remaining 40 million euro (£30 million) going to a company owned by Neymar's father, Neymar Santos. But investigations in Spain later showed that Barcelona spent nearly 83.3 million euro (£63.1 million) to acquire the Brazilian.

Neymar has also been facing problems with Brazil's tax office, which last year froze assets related to the player because of allegations of tax evasion. He has denied any wrongdoing in Brazil and Spain.

In an interview with Brazilian media on Sunday, he defended his father and contested the evidence being presented against them.

The 23-year-old striker helped Barcelona win a rare treble of Champions League, Spanish league and Copa del Rey titles last season.

He was also one of three finalists for the Ballon d'Or award won by teammate Lionel Messi. It was the first time he made it to the final short-list.

Messi is another Barcelona player set to appear in court in the next few months. The Argentine forward and his father will go on trial on May 31 - June 3 for allegedly defrauding Spain's tax office of 4.1 million euro (£3.11 million) in unpaid taxes from 2007-09. They have been charged with three counts of tax fraud and could be sentenced to nearly two years in prison if found guilty.

Barcelona defender Javier Mascherano recently avoided jail time after making a deal with prosecutors and the attorney's office after not properly paying taxes in Spain.