Messi’s failure to show for his medical underlined the 33-year-old’s determination to leave the club he has been with throughout his career.
The six-times world player of the year insists he has a clause in his contract that allows him to leave on a free transfer - a claim disputed by Barcelona and now by La Liga.
The ruling body said the only way a club can sign the Argentine forward is if he triggers a release clause of 700-million euros (M14 billion).
“In compliance with the applicable rule, La Liga will not approve a request to be de-registered as a player with the Spanish football federation, unless the amount in the release clause has been paid,” La Liga said.
Reuters footage showed players arriving for coronavirus tests on Sunday morning and Messi did not appear. He had been due at Barcelona’s training ground at 10.15am local time but a club source confirmed to Reuters he had not arrived.
La Liga’s stance is a blow to Messi’s hopes of a quick departure and to those clubs wishing to sign him.
Premier League Manchester City are the favourites which would allow Messi to link up with his former Barcelona coach Pep Guardiola but even the Abu Dhabi-owned club might find a 700 million-euro fee, plus Messi’s huge salary, a deal-breaker.
Messi, who has won more than 30 major trophies with the Spanish club and scored more than 600 goals, earns around one million euros per week.
He informed Barca on Tuesday he wished to leave immediately, plunging the club into new turmoil less than two weeks after their humiliating 8-2 Champions League quarter-final defeat by Bayern Munich.