Barcelona superstar Lionel Messi has reportedly demanded that an unprecedented clause be penned into his next contract for the Spanish club which will allow him to leave the club for his hometown team Newell's Old Boys whenever he wants.

The Argentine captain has repeatedly said that he wants to finish his career at the club where it all began for him some 22 years ago and he is looking to secure a deal which will ensure that he will get his move on his own terms reports Diario Gol.

Messi moved to Barcelona in 2000 as a 13-year-old as they were one of the few clubs that were willing to pay for the growth hormone treatment which he required.

Both Newell's, where he was in the academy, and River Plate, who were interested in signing the young playmaker, were unable to afford $1000 per month for the treatment before Barcelona stepped in and took control.

Messi's contract is due to run out in 2018, so negotiations for the next one, his eighth contract since joining the Catalan club, are expected to begin shortly.

Newell's vice-president Cristian D'Amico said in August this year that he expected Messi back after the 2018 World Cup in Russia when the Argentine turns 31, although it seems they will have to wait a bit longer.