The potential appointment of Penny Green or Michael Lynk as the United Nations' Special Rapporteur on the Palestinian territories has prompted outrage around the world.
British lawyers have written to Foreign Office minister Baroness Anelay opposing both candidates, while members of the Canadian Conservative Party have sent a letter to Prime Minister Justin Trudeau, urging him to speak out against the move.
Non-governmental organisation UN Watch has also published a damning report outlining the pair's strongly anti-Israel background.
Ms Green, a professor of law and globalisation at Queen Mary University of London, was chosen by the UN Human Rights Council's Consultative Group as the top candidate for the position.
She has repeatedly urged her followers on Twitter to support the Boycott, Divestment and Sanctions movement, calling it the "best way to resist this criminal government", and accused the Jewish state of committing "ethnic cleansing of Palestinians in apartheid Israel".
Mr Lynk, the group's second choice, has said he wished to "isolate Israel," a country which he has also accused of "ethnic cleansing".
During a UNHRC meeting on Monday, Palestinian representative Ibrahim Khraishi said that the UN Watch - which he accused of being "tied to the Israeli secret service" - had convinced the council to delay the nomination.
This was denied by UNHRC spokesman Rolando Gomez, who said that the council's president, Choi Kyong-lim, was "still consulting with a wide range of stakeholders" and would make the announcement on Thursday.
"No decision has been taken on any postponement," he added. "There's a lot of commotion surrounding this appointment, but the president remains focused on the task at hand, which is to find a suitable candidate."
UN Watch executive director Hillel Neuer said that appointing Ms Green or Mr Lynk would be a "travesty of justice. They're not a little biased, they reek of bias."