Formal public announcement of a decision, policy, or intention.
The prime minister made a declaration of a state of emergency.
宣言 is a general declaration; 宣言発表 emphasizes the formal act of announcing it publicly.
発表 is a broad term for any announcement or release; 宣言発表 specifically refers to a formal proclamation.
Compound of 宣言 (declaration) and 発表 (announcement).