Ling was the Chairman of the Singapore Democratic Party in 1991 when, in a surprise result, he defeated the incumbent MP from the governing People's Action Party, Dr Seet Ai Mee, to win the constituency of Bukit Gombak at the general election. Ling won 51.4% of the votes in the constituency to Dr Seet's 48.6%. Ling was one of three SDP MPs to be elected – with the party's leader Chiam See Tong retaining his seat in Potong Pasir, and Cheo Chai Chen winning in Nee Soon Central. The leader of the Workers' Party, Low Thia Khiang, was also elected in Hougang, giving the opposition parties a total of four seats. At the previous election, Chiam had been the only opposition MP to win a seat, so the results were seen as a significant success for the opposition. In 1994, the SDP appointed Ling to take over from Chiam as the party's parliamentary leader after Chiam fell out with the rest of the party's Central Executive Committee. Chiam resigned as the party's Secretary-General and was replaced by Dr Chee Soon Juan. After he publicly criticised them, the CEC attempted to expel Chiam from the party, but he won a court case to prevent them from doing so on procedural grounds. Ling hit the headlines in 1996 after Chiam whispered something into his ear during a debate in Parliament, to which Ling loudly responded "Don't talk cock!". Ling was formally censured by Parliament for using inappropriate language in the chamber as a result of this. Chiam joined the Singapore People's Party after Parliament was dissolved ahead of the election, was re-elected as Potong Pasir's MP representing his new party. However, Ling was defeated in his bid to be re-elected as MP for Bukit Gombak at the 1997 general election, losing to the PAP's Ang Mong Seng. Ling won 28.4% of the votes to Ang's 65.1%, with Syed Farid Wajidi from SPP taking 6.5% of the votes. Cheo was also defeated in his re-election bid. The SDP was thus left with no seats in Parliament. For the 2001 general election, Ling's old seat of Bukit Gombak was abolished following boundary changes. Ling stood in Cheo's former constituency of Nee Soon Central, and was defeated by the PAP's Ong Ah Heng. Ling received 21.5% of the votes to Ong's 78.5%. At the 2006 general election, Ling contested the seat of Bukit Panjang. He won 22.8% of the votes, losing to the PAP's Teo Ho Pin who gained 77.2%. During the election campaign, he was threatened with a defamation lawsuit by Prime MinisterLee Hsien Loong and former Prime Minister Lee Kuan Yew as a result of an article published in the SDP's party newspaper. On 24 April 2006, Ling said that he would not apologise as he did not know about the article until it had been published. However he eventually agreed to a settlement and issued an apology for the publication the article.
