What steps should I take if I suspect my Dutch attorney breached client confidentiality by sharing information?

In the Netherlands a lawyer’s duty of confidentiality is a statutory and professional obligation, so if you have credible evidence that your attorney disclosed your client information to a third party you can (1) file a formal complaint with the Nederlandse Orde van Advocaten (NOvA) – the disciplinary body will investigate, may impose sanctions (warning, suspension or disbarment) and will inform you of its decision; the complaint can be submitted by you personally (no lawyer required) using the NOvA’s online 'klacht' form together with any supporting documents (email excerpts, letters, etc.); (2) pursue a civil claim for breach of confidentiality (art. 6:162 BW) to obtain compensation for any actual loss or moral damage caused by the disclosure; for this step you will generally need a lawyer because the claim must be filed in the civil courts and a professional will help quantify damages and navigate procedural rules; (3) if the disclosed data includes personal-data covered by the GDPR, you may also lodge a complaint with the Dutch Data Protection Authority (Autoriteit Persoonsgegevens), which can impose administrative fines on the lawyer or law-firm and order remedial measures; finally, you can seek an injunction to stop further dissemination of the information. While you can initiate the disciplinary complaint and the GDPR complaint yourself, engaging a lawyer is advisable for the civil damages claim and for advice on preserving evidence, calculating losses, and ensuring that any settlement or court action protects your rights effectively. Sincerely, A-i-c