Reports going rounds has it that Last week the striker’s legal representative Ricardo Cardoso threatened Chelsea with a lawsuit regarding the club’s treatment of the Spain striker, particularly their refusal to sanction his protracted return to Atletico Madrid.
And it is now understood the proceedings have begun, reports the Daily Mail.
Costa, who is not training at the club’s Cobham HQ, has accused Conte of informing he was no longer wanted via a text message during the summer.
Conte and Chelsea are adamant Costa was aware of the situation in January.
The Blues boss has insisted that it was decided in the New Year by Costa and his agent, Jorge Mendes, that the striker would leave the club in the summer.
On Friday, when asked if Costa will return, Chelsea boss Conte admitted: ‘I don’t know. There is no news.’
A Chelsea spokesman added: ‘Nothing to report on that.’
Costa’s former club Atletico Madrid is still the most likely destination but they have not been able to agree a fee. Atletico are also under a transfer embargo until January and do not want to have to pay him if they cannot play him.