Back in June, the watchdog signalled its intention to disrupt Sky's "market power" in the pay TV industry by regulating wholesale access to premium content.
In its consultation, the regulator proposed freeing up access to Sky's subscription video-on-demand movies and FA Premier League TV rights at around 30% cheaper than current pricing.
Writing in the Daily Telegraph, Darroch said that Ofcom has been "encouraged" by BT and Virgin Media to introduce the new wholesale model, which would "undermine Sky's ability to earn a fair return" and also limit incentive to make further investments in content.
Despite this assertion, Darroch stressed that Ofcom should be in "no doubt about Sky's willingness to wholesale its premium channels".
Back in December 2007, the satellite platform holder offered to enter into a wholesale arrangement with other secure TV platforms. Under this proposal, it was prepared to free up premium content to rivals at "substantial price discounts as a reward for success in selling our channels".
In return, Sky wanted to launch a pay TV proposition on digital terrestrial television, which Darroch believes would have been "good news" for consumers and the industry. However, he said that Ofcom rejected this proposal as it "wanted to pursue even deeper price cuts".
"So it is clear that Ofcom's proposed intervention is not about the availability of our channels to other providers. It is about a regulator's attempts to impose price controls on the marketplace," he continued.
"Sky invests £1.4bn a year in programmes, more than any other commercial broadcaster. We will fight to defend our right to earn a fair return on that investment. The value of our channels should be determined in the marketplace, not the regulator.
"If Ofcom succeeds in imposing wholesale prices which do not fully reflect the risks and costs in our business, the effect is a tax on Sky to subsidise BT and Virgin Media. That subsidy not only undermines Sky's incentives for content investment, but further reduces the chances of BT and Virgin bidding for rights themselves.
"With a guaranteed, knock-down price on offer from Ofcom, there would be no reason to consider taking the risk. The impact on British sport of reduced competition for broadcast rights would be all too predictable."
Darroch concluded by warning the regulator that "consumers only benefit if the UK is an attractive place for businesses to invest and take risks".
Therefore, he said that any attempts by Ofcom to reshape the TV industry would send a negative message to other operators about the "dangers of being found guilty of success".