The Editors Guild said it "condemns any attempt to muzzle the media".
The Central Bureau of Investigation (CBI) raided the offices of NDTV and the homes of its promoters on Monday in connection with an alleged case of financial misconduct.
NDTV denied any wrongdoing and accused the government of "a witch hunt".
The channel, which has often criticised Prime Minister Narendra Modi's policies, said in a statement that "the ruling party's politicians cannot stomach" its independence and fearlessness.
"The raid is merely another attempt at silencing the media," it said.
The CBI said it was investigating claims that the channel's promoters had "caused a loss of 480m rupees [£5.8m; $7.5m] to a bank".
The agency said NDTV founder Prannoy Roy and his wife Radhika took a loan of about 3.5bn rupees from ICICI bank in 2008 after pledging their entire shareholding (about 61%) in the company as collateral.
The CBI said a private complainant had accused NDTV's promoters of violating banking laws, which do not permit more than 30% of the share capital to be pledged as collateral.
It further added that the bank also gave the Roys a waiver of about 10% in interest payment, leading to the loss of $7.5m.
"Consequent undue advantage was accrued [to the Roys]. It was also alleged that the bank did not insist on recovery of the entire loan amount when the promoters had adequate source of funding," the agency said.
The channel said in a statement that the entire loan amount was paid in full seven years ago.
"Even though millions of rupees of dues have not been paid by several industrialists and no criminal case has yet been registered against any of them by the CBI," it said.
"NDTV and its promoters have never defaulted on any loan to ICICI or any other bank."
Several journalists have defended the network, saying the government was trying to silence the media through CBI raids.