Hailing the verdict, Raja had said: "I have felt somewhat vindicated all along even prior to this judgement because the beneficial results of my actions are evident to and being enjoyed by the nation's public (especially the poor)."
Raja said he had, in fact, brought a "revolution" in the telecom sector.
Singh, during whose tenure the alleged scam broke out, said Raja and his family "suffered greatly in this process (case)."
The senior Congress leader, a Rajya Sabha MP, said: "all your friends are greatly relieved that truth has prevailed."
He extended his new year greetings to Raja and members of his family.
Special CBI Judge O P Saini pronounced the judgment in the 2G scam which had rocked the Congress-led UPA-II government.
In its charge sheet filed in April 2011 against Raja and others, CBI had alleged that there was a loss of Rs 30,984 crore to the exchequer in allocation of 122 licences for 2G spectrum which were scrapped by the Supreme Court on February 2, 2012.