Although extra officers have been laid on for the potentially explosive west London derby on Saturday, they have not been issued with any specific guidance on whether action should be taken over the abusive chant.
QPR could instruct their stewards to eject fans caught singing the song from Loftus Road, but they declined to comment on Tuesday on whether they planned to do so.
Hammersmith and Fulham police insisted anyone found breaking the law would be arrested but were uncertain whether the Ferdinand chant could be considered a breach of Sections 4 and 5 of the Public Order Act or Section 3 of the 1991 Football Offences Act, which deal with racially-aggravated offences.
The song about Ferdinand emerged in response to allegations that Chelsea captain John Terry had used a racist slur against the Rangers defender on October 23, something for which he was subsequently charged.
The two players are set to face each other on Saturday, four days before Terry appears in court to protest his innocence to the criminal charge.
Just over a week after the match between the sides, Chelsea fans were clearly heard to chant "Anton Ferdinand, you know what you are" during the club's Champions League game at Genk.
The abuse, which appears to have racial undertones, was immediately condemned by the Blues, who vowed to do everything possible to identify those responsible and ban them from Stamford Bridge, something they would also do were there to be a repeat.
The club - who have yet to announce whether their Genk investigation has concluded - made a similar pledge after a small group of fans allegedly sung racist songs about Ferdinand on the train home from Saturday's game at Norwich.
A man was arrested on Sunday following a complaint from a member of the public, while police continued to look for other people involved in the alleged incident.
They would also be obliged to investigate any complaint made if the Ferdinand chant was sung at Loftus Road but doubt was cast today on whether that would actually lead to any charges.
Criminal law specialist Haroon Shah of City law firm Christian Khan said anyone arrested over the chant could successfully argue they were calling Ferdinand a liar or a bad footballer rather than being racist.
He told Press Association Sport: "I think the Crown Prosecution Service would have great difficulty charging anyone for saying, 'You know what you are'.
"It's a very subtle way of getting at Anton Ferdinand, sadly.
"Whoever has drafted the chant is very clever.
"Can we prove what they mean? The reality is no."
The CPS confirmed they would only bring charges if they believed there was a realistic prospect of conviction.
A spokesman said: "As with any case, there would have to be a police investigation and a file passed to us on which to make a decision."
Meanwhile, QPR also declined to comment on reports they had encouraged Ferdinand to shake hands with Terry before kick-off on Saturday but Press Association Sport understands both clubs will issue a joint statement to fans in the next 48 hours in a bid to lower tensions around the fourth-round tie.
