Tewari described Prime Minister Manmohan Singh as having the "most impeccable track record" without any iota of doubt on his integrity.
He said the Comptroller and Auditor General's (CAG) "presumptive conclusions" of alleged wrongdoing in coal block allocations covered the period 1993-2009, and during this time, "eminent individuals from other political parties had held charge of the ministry".
Tewari said summoning the prime minister for questioning "should be a principle across the board and not be an exception".
He said the United Progressive Alliance government had been "extensively open" and that all decisions taken by the prime minister go through a "vetting and filtering process before decisions are taken".
He termed the opposition Bharatiya Janata Party's push for questiong the prime minister on coal block allocations during the time he held the ministry is a "politicised move".
Meanwhile, Parliamentary Affairs Minister Kamal Nath said Prime Minister Manmohan Singh has nothing to hide in the coal block allocation controversy and will make himself available to the Central Bureau of Investigation (CBI) for questioning if it makes a formal request.
Kamal Nath told CNN-IBN that if the CBI takes a decision that it needs to speak to the prime minister, there was nothing wrong in it.
Manmohan Singh has also said he was open to any public scrutiny into his conduct in office and the opposition must give him a chance to hear him out.
"I try to answer all questions that have been raised. I have no desire to hide anything from parliament, whether it is the coal matter, or other matters," the prime minister had told reporters.
The CAG has estimated that lack of transparency in coal block allocations has caused massive loss to the exchequer.
Tewari declined to comment on Manmohan Singh backing Congress vice president Rahul Gandhi for prime ministership after the 2014 polls.
He said the prime minister has earlier too made the statement and it would not be appropriate to comment on it.