LONDON Apple Inc on Wednesday lost a bid to block a mass London lawsuit accusing it of hiding defective batteries in millions of iPhones by "throttling" them with software updates.

The tech giant is facing a lawsuit brought by consumer champion Justin Gutmann on behalf of iPhone users in the United Kingdom, which the Competition Appeal Tribunal (CAT) ruled can proceed.

Gutmann's lawyers had argued Apple concealed issues with batteries in certain phone models and "surreptitiously" installed a power management tool which limited performance.

Apple, however, said the lawsuit is "baseless" and that it strongly denies batteries in iPhones were defective, apart from in a small number of iPhone 6s models for which it offered free battery replacements.

The CAT ruled Gutmann's claim should be certified to continue, but that there was "a lack of clarity and specificity" in the case which needed to be resolved before any trial.

(Reporting by Sam Tobin; Editing by Sachin Ravikumar)