His wife is sarpanch of Umarpura village.
Singh, who suffered eight gunshot injuries, was returning from a gurdwara when he was attacked.
Police have filed a case against gangster Harmanjit Singh, his father Nirmal Singh and three others.
The Shiromani Akali Dal (SAD) has demanded a CBI inquiry into the political murder by the Jaggu Bhagwanpuria gang and said since the Director General of Police is helpless in taking action against the minister-gangster nexus, it would hold dharnas as well as approach courts to ensure justice for the victim.
Addressing a press conference in Chandigarh, Majithia said the political assassination of Gurdeep Singh was a direct result of threats being issued to him warning of dangerous consequences if he did not stop speaking against the minister-gangster nexus.
"A message has been sent to me that my close political associates will be targeted if I do not stop speaking for justice for former Akali sarpanch Dalbir Dhilwan who was also murdered in the same way like Gurdeep Singh," he told the media.
Majithia, who was accompanied by former minister Daljit Singh Cheema, said he had already approached DGP Dinkar Gupta, seeking action against the Jaggu Bhagwanpuria gang in November but immediately afterwards the gangster was given a clean chit by an Inspector General-level officer.
Stating that he would not be deterred from his goal of exposing those like Jails Minister Sukhjinder Randhawa, who is "patronising gangsters like Jaggu Bhagwanpuria", said: "We will expose this nexus and will not allow the state police to indulge in a clean chit operation."
( With inputs from IANS )