The TalkTalk Internet filter extensively praised by David Cameron is controlled by Huawei, the Chinese firm currently being investigated by the UK government.
The voluntary Homesafe system, which has been used by TalkTalk since 2011, allows parents to select what types of content they want to block, including social media, gambling and pornography.
On Monday, the prime minister said TalkTalk had taken "great leadership" introducing the system. However it is Huawei's UK based employees that determine what content is blocked by the filter, not TalkTalk.
In a recently leaked letter to the four biggest ISPs, Downing Street also praised a new system currently being trialled by TalkTalk which will force customers to choose whether to turn parental filters on or off.
UK and US officials have extensively accused Huawei of spying for the Chinese government. Despite the UK government last year ruling that Huawei is no threat to UK security, it has this month announced a review into the company's cyber security practices.
The investigation followed a report by the intelligence and security committee that argued Huawei's equipment could be used by the Chinese to commit espionage.
Their focus is on the company's company's cyber-security evaluation centre in Oxfordshire, which was set up by the company to ensure their products are no threat to the UK, something the committee sees as unacceptable.
The UK government's move came came days before the former CIA and NSA head, Michael Hayden, claimed to know of hard evidence that Huawei has committed espionage.
Huawei accepted the UK government review, announcing that the company "shares the same goal as the UK government and the ISC in raising the standards of cyber security in the UK".
However, in a signal that the firm is getting tired of the claims, the reaction to Hayden's comments was decisively less measured - two of the company's top execs told the US government to "put up or shut up".