Die Burger and Rapport - traditionally NP-supporting - together with right-wing intellectuals, have accused Mr de Klerk of selling out the Afrikaners' right to self-determination during the 1994 negotiations which ended white-minority rule.
The newspapers seized on comments made by Mr de Klerk on a recent visit to London and on old claims in a new book that the African National Congress (ANC) was surprised at how easily the NP caved in during the crucial negotiations.
Izak de Villiers, editor of Rapport, issued a rallying cry at the weekend, arguing that the "broad Afrikaans community must mount a recovery action as never before" in its history.
The campaign against Mr de Klerk - arguably the most vicious against an NP leader in more than 40 years - reflects panic and paranoia in the Afrikaner community which claims its language, culture, and identity are dying.
Disaffection is growing, reflected at one extreme by the bombings at Christmas by right-wingers and the recent arrest of ultra-nationalists on charges of stealing arms from an army base. Dissatisfaction is reflected more generally in polls which show a significant drop in support for the NP.
Yesterday, on the morning that the Cape Times reported that NP unity and De Klerk leadership were now on the line, Mr de Klerk came out fighting.
"It wasn't a defeat," he said of the 1994 negotiated transfer of power. "It was an historic accord which saved this country from a civil war ... I have nothing I am ashamed of and nothing to apologise for."
Mr de Klerk said the entire debate about what was won and lost in 1994 was "sterile". Rounding on other "white" parties who joined in the criticism, he mocked politicians who mustered but a fraction of the NP's votes and scorned the right-wing Freedom Front's preoccupation with the creation of an Afrikaners' Volkstaat in some corner of South Africa.
But Mr de Klerk admitted that the recent assault had a grass-roots base, saying it was a sign of frustration in a community which felt it was being "hounded". But to look for scapegoats was not the solution, he argued.
He urged Afrikaners to look forward. Despite recent failures by the party to form alliances with other minority parties, he stood by the idea that the NP could go into the next election at the head of an opposition alliance.
Analysts argue that the NP is too weighed down by the baggage of apartheid to lead a viable opposition or to attract sufficient black votes. Mr de Klerk said yesterday that he realised the harm apartheid had done South Africa. But he argued that the development of one-party government was "unhealthy" in a democracy. It is a message which rings rather hollow coming from a party which for decades brutally repressed all democratic movements.