The phrase "all its protestations" is correct and usable in written English.
It can be used when referring to someone's repeated claims or assertions, often in the context of denying something or expressing a strong opinion.
Example: "Despite all its protestations of innocence, the evidence against him was overwhelming."
Alternatives: "all its claims" or "all its assertions".
The mighty Sun has, despite all its protestations, been defeated by one small but core concern of feminism.
The Telegraph says: "For all its protestations about having a coherent and costed policy programme, too many of Ukip's policies remain little more than incoherent ambitions..
But the underlying reason; the reason the confrontations have blown up into all-out war so quickly is our now certain sense that Scaf – for all its protestations – doesn't intend to give up power.
For all its protestations, Spotify has answered that question on its new site, saying that the average payout to rightsholders for a single play of a track is between $0.006 and $0.0084.
Moreover, it is, whatever its protestations, remarkably well organised: it was able to conjure up between 10,000 and 20,000 practitioners outside the leadership's compound of Zhongnanhai in central Beijing on April 25th to ask for official recognition of their movement.
Despite its protestations that it is an independent, business-minded entity, it acts like any other government agency.
His proclivities serve particularly well in a work that, for all its luminous qualities, is quintessentially dark in its fears and, yes, militant in its protestations.
Its protestations were widely scorned.
Despite its protestations of traffic chaos, the roads appear eerily quiet by today's standards.
Israel is not alone in believing that Iran, despite its protestations, is secretly hard at work on a nuclear bomb.
Despite its protestations last year that the data scoop was done in error and voluntarily highlighted, it was handed the CNIL's maximum fine of €100,000 (£80,700).
