The task of taking on the National Party in Parliament was rewarded by the human rights and values enshrined in South Africa's post-apartheid Constitution, former opposition leader Colin Eglin said on Friday.
"The values for which we fought are entrenched in the Constitution. That is our greatest achievement," Eglin said as former Progressive Party stalwarts, or Progs, marked the 50th anniversary of its establishment at a function in the Old Assembly Chamber in Parliament.
He added however that the "Constitution can only work as well as the people who serve it and it is not working as well as it could. That is the fault of functionaries''.
Eglin became the leader of the Progressive Party in 1971.
It was "highly emotional" to recall the party political turmoil of the sixties and early seventies, when all Progs lost their seats, bar Helen Suzman who was the sole opposition Member of Parliament (MP) for 13 years.
"We took great risks, but it was very fulfilling because the risks came off."
Eglin, who served as an opposition MP for the Democratic Alliance until 2004, paid tribute to former Presidents FW de Klerk and Nelson Mandela for reaching out to each other to build a cohesive nation.
"When we started negotiating we had sitting in Tuynhuys a white nationalist leader who negotiated before he lost and a black nationalist leader who negotiated before he won.
"That synergy opened a window of opportunity."
Democratic Alliance leader Helen Zille said the "Progressives contributed in their time and context to taking the next step in building a non-racial, democratic South Africa.
"It is a project that will never be over, and which has required as much work after 1994 as it did before."
Zille said the official opposition remained true to the non-racial vision articulated by Jan Steytler, the first leader of the Progressives, on November 13, 1959.
Steytler said: "In future, colour and colour alone should not be the yardstick by which people are judged. We consider that all South Africans should be given the opportunity to make a contribution to the political and economic life of our country.
"We want to face the future, not with fear, but with confidence that we can live together in harmony in a multi-racial country."
Zille said in the grip of apartheid, Steytler's words were "radical, subversive even, coming from a white South African.
"In fact, today we look back on Jan Steytler's words and realise that he was more than 50 years ahead of his time."
She said that vision was under threat from powerful figures who failed to understand the true values of democracy.
"There are many powerful people in South Africa today who do not understand constitutionalism, who make no distinction between the party and the state, and who believe winning an election gives you the right to exercise untrammeled power."
Former Progressive Federal Party MP and Democratic Party founder member Harry Schwarz paid tribute to Zille, calling her the embodiment of the principles they fought for.