The tech firm says Britain's proposed laws leave 'the back door' open for criminals and terror groups
"The fact is to comply with the government's proposal, the personal data of millions of law-abiding citizens would be less secure."
Apple reserved its strongest words for the bill's lack of clarity towards the encryption of data. Encrypting data means scrambling, making it much harder to read. Services like e-commerce and banking rely on encrypting financial details to keep them secure.
Increasingly, messaging and communications service - including Apple's iMessage and Facetime, but also Facebook and WhatsApp - encrypt user data.
Apple has also warned that because it is based in Ireland - the UK is trying to legislate for companies outside its jurisdiction - adding, "If the UK asserts jurisdiction over Irish or American businesses, other states will too."
Andrew Parker, director general of MI5, has said encryption is making it harder for security services to find terrorists' communications.
The British government said it does not want to weaken encryption, but the bill can require companies to hand over data 'in the clear', ie with encryption removed.
Apple is so alarmed, it voluntarily made a written submission to the committee scrutinising the bill.
It wrote: "Strong encryption is vital to protecting people from malicious actors.
"Without strong defence, these attacks have the potential to impose chaos, and threaten our way of life, economic stability and infrastructure.
"This bill threatens to hurt law-abiding citizens in its effort to combat the very few bad actors who have a variety of ways to carry out their attacks.
"Strong encryption does not eliminate Apple's ability to give law enforcement metadata or other categories of data … the information Apple and other companies provide helps catch criminals and save lives."
Apple also attacked proposed requirements for private companies to help the government with 'equipment interference' - the legalistic term for hacking by the state.
The Investigatory Powers Bill joint select committee has until 11 February to scrutinise the proposed legislation and interview expert witnesses.