"Reading part of the interrogation of Mr Abdeslam at a press conference constitutes a violation," lawyer Sven Mary told Belgian newspaper Le Soir.
His client, who was captured in Brussels on Saturday, will lodge a legal complaint against Molins on Monday, he said, noting that there seems to be a "difference of culture between Belgium and France on press statements by magistrates" but insisting that French officials are bound by Belgian rules while Abdeslam is held in Belgium.
Prosecutors in both Belgium and France are allowed to breach confidentiality in certain circumstances - in France "to avoid the spreading of partial or inaccurate information or to end disruption of public order" and in Belgium when authorised to give an update on an inquiry.
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Mary has said that Abdeslam, who has been charged with "terrorist murder" and participating in a terrorist group, will fight attempts to extradite him to France.
A decision on extradition must be made within 60 days following an arrest, or 90 days if it is taken to higher courts, according to the French Justice Ministry.
Abdeslam held in maximum-security prison
Abdeslam was taken to a maximum-security prison in the Belgian city of Bruges after being interrogated on Saturday.
He is to be held in the "individual and special security" wing, built in 2008 for prisoners who pose an escape risk or who have specific behavioural problems, where cell number eight had been reserved for him for some time, according to France Info radio.
The unit is heavily guarded and all cells have double doors, furniture is bolted to the floor and television sets are housed in plexiglas.
Mehdi Nemmouche, who carried out a fatal attack on the Brussels Jewish Museum in 2014, has been held there since being extradited from France, where he was caught.
Abdeslam's accomplice, known by two false names - Mounir Ahmed Alaaj and Amine Choukri - , is being held in a prison near Liège, eastern Belgium, after being arrested at the same time as his friend.
Phone, pizzas led to capture
Sources have now revealed that Abdeslam was located via his mobile phone after an acquaintance informed police that the suspect had called him to ask for help in finding a new hideout after Tuesday's raid on a flat where he had been holed up.
Their belief that they had found him was confirmed by the large number of pizzas being delivered to the address they were watching, according to reports.
French Interior Minister Bernard Cazeneuve has beefed up the police presence on the Belgian border following Abdeslam's arrest, having already posted 5,000 officers there after the 13 November Paris attacks.