Lebelo was testifying in the constructive dismissal case between Sars and former revenue service spokesperson Adrian Lackay in Johannesburg on Tuesday.
Lebelo said investigations were not initially conducted, but that things changed when Sars Commissioner Tom Moyane arrived.
Moyane had given instructions to change the system and told IT to block the use of Gmail accounts, Lebelo said.
"Our people [employees] received news flashes and they forwarded them to their friends. There was no investigation into the leaks," Lebelo said, in what was his second day before the Commission for Conciliation, Mediation and Arbitration (CCMA).
He added that if Sars wanted to "get rid" of Lackay, they would have sent him to a disciplinary hearing after he had forwarded confidential emails to his wife.
Lebelo said Lackay and the media had created an impression that Moyane was failing and, as a result, people were leaving the service.
He was responding to allegations made by Lackay that about 55 employees left Sars.
"I want to put it on record that it is a lie and none of the 55 people left Sars. It was only a handful of less than 10 people who have left Sars for different reasons.
"Media including Mr Lackay are in a tirade to create an impression [that] Moyane ... is failing and, as a result, people are leaving Sars," Lebelo said.
Moyane has gone beyond his targets since arriving at Sars, he added.
On allegations that Sars opened a criminal case against former commissioner Ivan Pillay two weeks after he left, Lebelo said this was not true.
He said the case was opened in May 2015 after two employees confessed to having been paid to install cameras at the Hawks and police offices.
Lackay had previously revealed much of what went on behind the scenes at Sars when Moyane first started the job amid the onslaught of the rogue unit debacle in 2014 and 2015.
He had said his working conditions became unbearable amid allegations of the rogue unit's existence and that he was forced to leave after it became untenable to associate with the goings-on at the revenue service.
The number of journalists in the CCMA boardroom dwindled from January, when Lackay first gave evidence, and they missed Lackay's revelations that not only did Moyane not fight back against the rogue unit allegations but he "tacitly approved them".
Lackay went a step further, saying that Moyane's right-hand man at the time, acting chief operating officer Jonas Makwakwa, said at a Government Communication and Information System (CGIS) meeting that Lackay was a problem in the communication department at Sars because he was denying that a rogue unit existed. Makwakwa was suspended after it emerged that there were suspicious transactions on his bank account.
But Lebelo rubbished the claims.
He said they went to the GCIS meeting to get guidance regarding problems they experienced with the media. He added that Moyane was under attack from the media.
Lebelo said that at no point has anyone said Lackay was a "problem".
Lackay had also said that Moyane changed offices, making himself inaccessible and that he (Lackay) was increasingly being left out of the loop on important events at Sars, such as the suspension of deputy commissioner Ivan Pillay, at a time when, as the spokesperson of the organisation, the media were bombarding him with questions. - News24