The Supreme Court found Salwai had misled the court when he said the Council of Ministers had approved a decision to create parliamentary secretary positions.
The case was brought by then-opposition leader Ishmael Kalsakau in November 2019, who said the council had never approved it.
During the trial however Kalsakau, who is now Deputy Prime Minister, admitted the council had approved the posts in 2013 but only for the Office of the Prime Minister and not for other ministries as Salwai had claimed.
Salwai and two other former MPs were last week acquitted of 10 other bribery and corruption charges related to the appointments.
Salwai is set to be sentenced on 3 February.