A teacher who was found not guilty of a racially aggravated public order offence after holding a placard at a pro-Palestine protest depicting Rishi Sunak and Suella Braverman as coconuts has made a complaint to the CPS and police watchdog.

Marieha Hussain denied the prosecution’s allegation that the placard was “racially abusive” and her trial at Westminster Magistrates’ Court heard that she “quite obviously does not have a racist bone in her body”.

Ms Hussain was acquitted of the charge on September 13, and has now made complaints to the Crown Prosecution Service (CPS) and Independent Office for Police Misconduct (IOPC).

During the trial, prosecutor Jonathan Bryan said: “Coconut is a well-known racial slur which has a very clear meaning.

“You may be brown on the outside, but you’re white on the inside. In other words, you’re a race traitor – you’re less brown or black than you should be.”

Rajiv Menon KC, defending, said the placard was “not abusive”, but a “political criticism” of then-prime minister Mr Sunak and then-home secretary Ms Braverman.

Clearing Ms Hussain, district judge Vanessa Lloyd said: “I find that it was part of the genre of political satire and, as such, the prosecution have not proved to the criminal standard that it was abusive.

“The prosecution has also not proved to the criminal standard that you were aware that your placard may be abusive.”

A statement from solicitors Gareth Peirce and Sajida Malik confirmed the complaints were made and said the Metropolitan Police and CPS “failed inexcusably in their respective responsibilities, seriously undermined the exercise of free speech and exposed Ms Hussain to irreparable harm”.

Ms Hussain told the Guardian: “It has damaged my reputation and lost me my career. They must answer for the harm they have caused not just to me but equally the right to peaceful protest.”

The statement from the solicitors says: “We confirm that last week serious complaints were made to the Independent Office for Police Conduct (IOPC) and to the Crown Prosecution Service (CPS) in respect of a prosecution that went forward despite unsound evidence and in the face of clear contrary legal principles.

“That Ms Hussain was acquitted was a relief shared by her lawyers. That she should ever have faced trial remains, however, unfinished business.

“The Metropolitan Police and the CPS failed inexcusably in their respective responsibilities, seriously undermined the exercise of free speech and exposed Ms Hussain to irreparable harm.”

The solicitors criticised the force for responding to a picture of Ms Hussain with the placard posted online by what they called an “anonymous right-wing American-based organisation with a known agenda of extreme hostility towards Palestinian campaigners”, saying the force was “actively looking” for her.

And they said the “Met Police internal emails produced by the case officer confirmed that independent expert evidence (that the use of a ‘coconut’ motif could constitute a racial slur) had been thought necessary by the CPS for any prosecution to proceed, but no such evidence was ever obtained”.

Their statement adds: “The complaints filed on Ms Hussain’s behalf raise detailed questions with both organisations – what happened in the police command room on the day of the demonstration? What influences were at work in decision-making? What responsibilities were considered or ignored? What understanding was ever sought of the context of Ms Hussain’s protest and of the use of the symbol itself? And, above all, what consideration was given:

“To the exposure of Ms Hussain to irreparable harm;

“To the protection guaranteed for free speech within UK legislation, common law, and the European Convention (above all for political criticism demanding the highest degree of protection);

“To the chilling effect that Ms Hussain’s prosecution has had on protected speech, and, more than any other, on its exercise by communities centrally involved in Palestinian protest?”

The CPS said a complaint has been received and it will be considering its content and responding to it.

A spokesperson said: “Our prosecutors reviewed this case carefully and concluded there was enough evidence for it to be presented to a court.

“The defendant was found not guilty and we respect the judge’s decision.”

A spokesperson for the Met Police said: “We have received a complaint via the Independent Office for Police Conduct, and this is currently being recorded and assessed.”