During the Repnin Sejm in 1767, Sołtyk opposed the practical dictatorship of Repnin, and for this opposition he was arrested and imprisoned in Kaluga, along with three other Polish senators (Józef Andrzej Załuski, Wacław Rzewuski and Seweryn Rzewuski). Sołtyk was a vocal opponent of giving non-Catholics equality with Catholics, and he issued a manifest calling for prayers for preservation of the faith and national freedoms which initiated Bar confederation.