Apple has warned that a British plan to give intelligence agencies extra online surveillance powers could weaken the security of personal data for millions of people and paralyse the tech sector.

Britain unveiled proposals for new online powers last month that it said were needed to keep the country safe from criminals, fraudsters and militants, including the right to find out which websites people visit.

Critics however say the Investigatory Powers Bill gives British spies authority beyond those available in other Western countries, including the United States, and that it constitutes an assault on personal freedom.

"We believe it is wrong to weaken security for hundreds of millions of law-abiding customers so that it will also be weaker for the very few who pose a threat," the iPhone maker said.

Apple submitted its response to a British parliamentary committee that is scrutinising the new bill in the latest clash between Western governments seeking to monitor the threat from Islamist militants and online companies working to maintain security.

Apple said the draft laws could weaken data encryption, sanction interference with its products, force non-UK companies to break the laws of their home countries, and spark similar legislation in other countries that could paralyse firms under the weight of dozens of contradictory laws.

Lending support to Apple's view, Microsoft also said an international approach would keep people more secure than competing measures from different countries.

"The legislation must avoid conflicts with the laws of other nations and contribute to a system where likeminded governments work together, not in competition, to keep people more secure," a spokeswoman said.

Apple said in its submission an attempt to force non-UK companies to take action that violated the laws of their own countries "would immobilize substantial portions of the tech sector and spark international conflicts".

The British government, which failed with a previous attempt to increase online surveillance dubbed the "snoopers' charter", has said the proposals will not ban encryption or do anything to undermine the security of people's data.

But Apple said proposals in the new bill would weaken encryption, such as the explicit obligation on service providers to help intercept data and hack suspects' devices.

The California-based company, which uses end-to-end encryption on its FaceTime and iMessage services, said the best way to protect against increasingly sophisticated hacking schemes and cyber attacks was by putting into place increasingly stronger -- not weaker -- encryption.

"In this rapidly evolving cyber-threat environment, companies should remain free to implement strong encryption to protect customers," it said.

As well as being able to carry out bulk interception of communications data, the bill would also allow the security services to perform "equipment interference", whereby spies take over computers or smartphones to access their data.

In its submission to the draft bill, Apple criticised any such requirement to create "backdoors" that could weaken the protections built into Apple products.

"A key left under the doormat would not just be there for the good guys," it said. "The bad guys would find it too."