MIDDLESBROUGH dropped a legal bombshell on Derby County just days before the Rams' Championship play-off final.
The Teesiders informed the club they plan to sue them over a Financial Fair Play breach.
Boro chairman Steve Gibson dramatically vowed to take legal action against the Rams - alleging their owner Mel Morris clearly broke the rules.
According to the Telegraph, officials from the Riverside club called Derby on Friday and informed them of their intention to sue despite it being just days before the Rams' multi-million-pound Wembley clash with Aston Villa.
The alleged breech of profitability and sustainability rules is said to have infuriated Boro after the midlands club reported a £14.6million profit in their 2017/18 accounts after Morris sold the club's Pride Park stadium only to lease it straight back.
While Gibson is resolute in his cause, County are sure they have done nothing wrong but were shocked at the timing of the notification.
Boro finished just one place outside the play-offs - just a single point behind Derby who snuck into sixth.
Gibson is looking for a new manager and recently spoke to John Terry having parted company with Tony Pulis just over a week ago.
But he does not look likely to let that stop him in his crusade for justice.
However, Morris has also been sturdy in his stance reminding the North-East club that their officials were invited to look at Derby's accounts during an EFL club meeting in March.
Morris said: "Middlesbrough were offered by us in writing to come with their advisers to go through our submissions for profitability and sustainability but they declined."