Van Eck was born in Holland on 18 December 1943, the first born of five children. He came to South Africa when he was five years old with his mother and father, a classical piano teacher.
He matriculated at Bonnievale High School in 1961, after which he studied at the University of Stellenbosch, obtaining a BA degree majoring in geography and history in 1964, a secondary teachers' diploma in 1965 and a BA (Hons) in geography in 1965.
It was at university that he started to seriously challenge his National Party upbringing and joined the (then) Progressive Party. When he joined the Progressive Party, Colin Eglin asked him to take the party's views into the Afrikaans areas. Van Eck concentrated on students. He did this in his capacity as founder-editor of the Progressive Party's Afrikaans journal Deurbraak (meaning "breakthrough").
Until 1985, Van Eck held the positions of national public relations officer, national director of publications and editor of various publications for the then Progressive Reform Party (PRP) and the Progressive Federal Party (PFP).
In 1974 and again in 1977 he stood unsuccessfully as a parliamentary candidate and a provincial council candidate for the Progressive Party. During his time as a party employee, he married Eunice, who was then working as national secretary of the PRP.
He was elected to the Provincial Council for the PFP in Groote Schuur in 1981, and became a PFP MP for Rondebosch in a 1986 by-election. He worked as a city councillor for Cape Town from 1985 to 1988.
In 1987 Van Eck was re-elected unopposed as MP for Claremont. He resigned from the PFP in August 1987 and remained as an independent in Parliament.
Inside Parliament, Van Eck went straight for the jugular of successive presidents and ministers of law and order. He repeatedly embarrassed, shamed and infuriated the ruling party. It had no answer other than to banish him from Parliament from time to time.
Van Eck’s fearless, strident and relentless pursuit of justice was not fully supported by the Progressive Federal Party (PFP), so he resigned from that party and represented Claremont as an independent from 1987 until 1989. Consequently, his candidacy as a Democratic Party (DP) MP in 1989 was controversial. In 1992, he represented the DP at the Codesa talks.
In 1992, he joined the ANC together with four other Democratic Party MPs. As a Member of Parliament, Van Eck was one of the first sitting MPs to join the ANC after the organisation was unbanned in 1990. He left the then-Democratic Party to join the ANC long before the first democratic elections in 1994 and served the ANC until 1999.
Among a group of South African "Whites in a changing South Africa" to visit the then-ANC headquarters in Lusaka, Zambia, in July 1989, Van Eck and the group that included religious leaders, intellectuals, city councillors, trade unionists, students and journalists, were praised by late ANC leader Oliver Tambo for braving arrest to meet the banned organisation. The gathering was convened under the auspices of the Five Freedoms Forum and the ANC.
"There are many among us who deserve a special accolade -- they are parliamentarians, including Parliament's unfading star, the indefatigable Helen Suzman and the go-getting Jan van Eck," Tambo told the gathering.
He entered Parliament as an MP for the Progressive Federal Party, and investigated police brutality. Van Eck was expelled from Parliament for six months after refusing to withdraw his claim that state agents were behind township attacks. At the height of repression, and with the press unable to report on security issues, Van Eck used Parliament to demand answers regarding the disappearance of political activists - most notably Stanza Bopape from the Mamelodi Civic Association. His persistence resulted in even the New York Times reporting on the matter. The Truth and Reconciliation Commission testimony showed that he was right.
Van Eck left Parliament in 1994 and for the next 12 years worked tirelessly on peace efforts in the Great Lakes region to find a solution to the Tutsi-Hutu civil war that had for years wrecked that country's political and economic stability. He played a significant role in brokering dialogue, building confidence and breaking down political and ethnic stereotypes in Burundi.
Van Eck won many accolades, including the "Paul Harris Fellow" by the Rotary Foundation of Rotary International "in appreciation of tangible and significant assistance given for the furtherance of better understanding and friendly relations among peoples of the world".
Van Eck, died of a heart attack in Cape Town at the age of 65 on 27 January 2009.
Burundian peace facilitator and former MP, Jan van Eck, was a "peacemaker" and a "son of South Africa and a man who mastered the art of listening.", ANC Treasurer-General, Mathews Phosa, said at his funeral. Not many people were aware of the enormous role that this quiet, but competent Afrikaner and African, played in Burundi. "He succeeded with other mediators to turn decades of hate and violence into a willingness to talk."
Others who paid tribute to Van Eck included Archbishop Emeritus Desmond Tutu, Elie Bagona, chair of the Burundian community in Cape Town, Di Bishop, who was his "benchmate" in the provincial legislature, former MP Colin Eglin and Stel Snel, who worked with Van Eck and in the 1980s helped him at the Umac (Unrest Monitoring and Action Committee).
He is survived by his wife, Eunice and three children.