The hearing was to take place on Tuesday.
No hearing on the matter has taken place since December 2016 despite clear instruction from the Delhi High Court in 2014 to dispose of the matter within 6 months.
The hearing scheduled on February 20 has been cancelled "due to unavoidable circumstances", according to a Central Information Commission notice.
Information Commissioner Sridhar Acharyulu had recently questioned Mathur on the lack of transparency in formation of benches to hear the matter and delay in completing the hearings, sources in the CIC said.
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When contacted, Acharyulu said it was an internal matter.
A three-member bench headed by Acharyulu had heard the matter in December 2016. A few days later, one of the Information Commissioners on the bench, Bimal Julka, had recused himself citing pending work. Mathur had then put the matter in abeyance.
Meanwhile, Acharyulu's order directing Delhi University to give records related to all the students who had passed BA degree in 1978, the year in which, according to the varsity, Prime Minister Narendra Modi had also cleared the examination, became public.
Mathur constituted a four-member bench in July last year but no member of the bench which had heard the matter for nearly five months found place on it.
The move drew sharp reaction from R K Jain, the complainant, who questioned the rationale behind the new bench, prompting Mathur to defer the hearing for seeking legal opinion.
"The new four-member bench does not have any member with legal qualifications and experience in the field of law," Jain had claimed.
It is against the apex court's directives, he had added.