Mr Mahmud Awang, one of the founders of the National Trades Union Congress (NTUC) and its first caretaker president, died on Monday. He was 93.

Mr Mahmud, a former People's Action Party (PAP) MP, was a prominent unionist who laid the foundations for Singapore's pragmatic approach to union issues and helped workers here improve their wages and working conditions.

Born in Kluang, Johor, in 1928, he moved here during World War II as one of many young men compelled by the Japanese occupying forces to work at their naval school in Sembawang.

He went back to Kluang after the war but returned to Singapore to find work. He then joined the Singapore Traction Company (STC) as a bus conductor.

In a condolence letter yesterday to Mr Mahmud's son Endut, Prime Minister Lee Hsien Loong said Mr Mahmud was one of Singapore's founding leaders and a stalwart in the fight against the communists.

Mr Mahmud got involved in union work at STC, and became close friends with Mr Ahmad Ibrahim, Mr Devan Nair and Mr Lee Kuan Yew during that time.

He was elected president of the Singapore Traction Company Employees' Union, and later became president of the Singapore Trades Union Congress (STUC).

When the then MP for Anson, Mr Baharuddin Ariff, died in 1961, Mr Mahmud was approached by Mr Ahmad, a Cabinet minister, to stand as a candidate in the by-election.

He agreed, and narrowly lost to former chief minister David Marshall by about 500 votes after six of the 10-member STUC secretariat issued a statement that called into question the PAP Government.

That precipitated the split in the PAP, when 13 PAP assemblymen crossed the floor to form the Barisan Sosialis, PM Lee wrote in his letter.

The STUC also split, with the pro-PAP unions - including the Singapore Traction Company Employees' Union - forming the NTUC.

Mr Mahmud became chairman of the NTUC's pro tem committee.

"He belonged to the small group of unionists who held the line against the leftists, and eventually persuaded workers to cast their lot with the PAP," PM Lee said.

In 1963, Mr Mahmud again stood for election to the legislative assembly in Kampong Kapor, and won the seat for the PAP.

He served as an MP for the next five years, stepping down in 1968.

In the two years when Singapore was part of Malaysia, Mr Mahmud was among the Malay PAP leaders who came under "fierce and relentless pressure" by Umno politicians to choose race over nation, PM Lee said.

"But Encik Mahmud and his comrades embraced the nobler dream and held firm in their conviction.

"Because of their courage and leadership, the vision of a multiracial Singapore was kept alive, and is today a reality."

Singapore's founding prime minister Lee Kuan Yew was forever grateful for Mr Mahmud's stout-hearted support at this critical moment in the Republic's history, and they kept in touch, PM Lee added.

"We were honoured that Encik Mahmud was one of the pallbearers at Mr Lee's funeral in 2015."

In a letter sent to Mr Mahmud's family, NTUC president Mary Liew and secretary-general Ng Chee Meng said the labour movement is saddened by his passing.

They noted that Mr Mahmud was an early champion of Singapore's unique tripartism approach, which has given the country its competitive edge.

"Without pioneer union leaders such as Brother Mahmud, Singapore would perhaps not be able to stand apart or even transform from Third World to First," they said.