In July, home ministry had told court it has directed police to carry out a probe into allegations.
A preliminary enquiry has been initiated by Delhi Police into allegations of tapping of phones of politicians, bureaucrats, industrialists and many other high-profile people by corporate major Essar Group.
Lawyer Suren Uppal, the complainant in the case, has been asked to present himself before the Special Investigation Team of Delhi Police on September 10.
Mr Uppal had filed a plea in the Delhi High Court in June alleging that Essar tapped phones of a number of high-profile persons including some Union Ministers. He had also approached the Prime Minister's Office against the group in the case.
The lawyer had alleged that the Essar Group had ordered its former security chief Albasit Khan to tap telephonic conversations of its business rivals when Atal Bihari Vajpayee was the Prime Minister.
In July, the home ministry had told the Delhi High Court that it has directed police to carry out a preliminary enquiry into the allegations Mr Uppal had made in his petition.
In a letter to Mr Uppal on September 2, a Deputy Commissioner of Police had asked him to join the probe being carried out by the SIT, a senior Delhi Police official said, refusing to share further details.
When contacted, Mr Uppal claimed he has a lot of documentary evidence including log books, handwritten notes as well as recordings of some top politicians and other high-profile persons to back his charge that the corporate major indulged in phone tapping from 2001 to 2005.
"I am ready to join the probe and present myself before the police committee on the given time and date. I have received just a letter asking me to join the probe. I have a lot of documentary evidences including some CDs that I have not given to anyone so far," he said.
Sources said that the SIT, led by a special commissioner, is expected to file a case after it wraps up its preliminary probe.
The five-member SIT is likely to call many persons to join the probe.