Speculation over the former Charlton and West Ham United midfielder’s future at Fratton Park has run rampant after Danny Cowley initially invited the free agent to train with the club in June and last month said a deal was still possible.
This month chief executive Andy Cullen also said Mingi was ‘one potentially for the long term’ as his time at PO4 was discussed.
But now the 20-year-old’s solicitor has written to the Blues claiming a contract had already been signed by former chief executive Mark Catlin in the summer.
Mingi supposedly played for Pompey in pre-season while complaining of a groin injury and underwent rehabilitation with the club for six weeks until the end of August, after a scan revealed a grade 2 hip flexor tear.
In a legal letter, dated September 9 and seen by The News, Mingi claims he was declared fit to return to action but then told he could find another club, with the League One side denying a deal was ever done.
Mingi had remained at the club’s Roko training base to help his recovery and get fit, meeting with the medical team on a near-daily basis to recover from his injury - and was shocked to be ditched.
He now wants £3,500 in back pay dating to his 60-minute appearance in the Bristol City friendly on July 20, and for the club to register him with the English Football League, essentially agreeing a contract exists.
If this doesn’t happen the West Ham academy product will take the case to an employment tribunal, the EFL’s Player Related Dispute Commission or seek other avenues for a resolution.
A Blues spokesman said: ‘Portsmouth Football Club are in dialogue with a summer trialist over a personal matter.
‘As with all matters of a personal nature, these discussions remain confidential.’
The legal letter also claims his injury was aggravated by Pompey playing him against the Robins and in the St George's Park friendly against Burton Albion four days later, despite having complained of groin pain.
Summer triallist Mingi arrived at Fratton Park from Charlton on June 28, playing for 45 minutes against both QPR and the Hawks as the Blues began their pre-season preparations.
His trial period was extended from two to three weeks and - according to his lawyer - was due to be unveiled as a new signing on July 22 after terms of a contract were agreed and a medical passed.