noun
written proposal; recommendation; memorial
A formal written proposal or recommendation, typically submitted to a government body or authority. The term carries a bureaucratic or official tone.
市民団体が環境政策に関する建議書を市長に提出した。
A citizens' group submitted a written proposal on environmental policy to the mayor.
審議会は政府に対して建議書をまとめた。
The advisory council compiled a recommendation for the government.
勧告 is a recommendation or advice, often verbal or less formal, whereas 建議書 is a formal written document.
建議 (proposal, recommendation) + 書 (document). The exact historical derivation is uncertain, but the compound follows standard Sino-Japanese word formation.