The train had mowed down a crowd in Joda Phatak, Amritsar, on October 19, 2018, that had gathered on the railway track to watch Dussehra celebrations, where she was the 'guest of honour'.
The probe report, made public by the Punjab Human Rights Organisation (PHRO) on Saturday, has also raised questions over the loco pilot's role.
Endorsing the report on Monday, Shiromani Akali Dal (SAD) leader Manjinder Singh Sirsa said: "It stated that no permission was taken as Sidhu's close aide Saurabh Madan Mithoo was the organiser. It was an accident of multiple errors."
Sirsa also blamed the Punjab Police and termed it a major "goof-up" on the part of the police and the municipality for letting crowd gather on a railway track, and also granting permission to organise an event there.
The SAD leader also accused Sidhu's wife of using her "VIP influence".
"The report has stated how the VIP influence (Navjot Kaur Sidhu's name) was used for the permission and the authorities, like the police and the municipal corporation, didn't pay any heed because of the VIP guest," he said.
Though the incident had Sidhu's wife under the scanner, she was given a clean chit last year by a magisterial probe, ordered by the Congress-led government.
The probe, conducted by Jalandhar Divisional Commissioner B. Purushartha, had indicted Saurabh Madan Mithoo, son of a Congress councillor in Amritsar and a close political aide of the Sidhu couple, and officials of the Amritsar Municipal Corporation, local administration, the police and railway authorities for the tragedy.
( With inputs from IANS )