In March 1984, Tan was sacked as vice-president from the MCA along with Lee Kim Sai as well as other members for urging the party to investigate its member records for the presence of non-existent people, an issue that had sparked off factionalism and crisis within the party. However, he and the other 13 were all reinstated two months later with the support of 1,600 MCA members in an extraordinary general meeting. In November 1985, he was voted to be president of the MCA winning 76.9% of the votes cast, the largest majority in the party's history, and the first challenger since 1954 to win national leadership.