The English Football League (EFL) has asked Derby County's administrators to provide a funding plan to show how the club can fulfil their remaining second-tier Championship fixtures, a spokesperson for the governing body said on Friday.
The request was made after an EFL board meeting on Thursday, a statement said, with Derby now effectively under a transfer embargo as they will not be able to sign players or extend contracts before providing proof of funds.
Derby, managed by former England and Manchester United striker Wayne Rooney, entered administration in September amid continued financial difficulties.
The club has been under a transfer embargo since before last year's summer transfer window after failing to pay player wages, which meant they have only been allowed to sign free agents with strict limits on wages.
"The EFL has written to the administrators reiterating that it needs confirmation as a matter of urgency of how they intend to trade whilst Derby County remains in administration, including a funding plan that will enable the club to fulfil its fixture obligations until the end of the current season," the statement read.
"Without this visibility, the League is unable to approve any player signings or renew existing registrations and this position had been communicated to the club prior to yesterday's meeting.
Derby confirmed on Friday that 39-year-old defender Phil Jagielka, who joined the Midlands outfit on a short-term basis in August, has left the club after his contract expired.
"Talks had been ongoing with Jagielka to extend his stay at Pride Park Stadium in recent weeks but because of the restrictions the club is operating under he has unfortunately been unable to put pen to paper," the club said.
Derby are bottom of the table and 11 points adrift of the safety zone after being docked 21 points for entering administration and breaching the EFL's financial rules.
Sky Sports reported last week that former Newcastle United owner Mike Ashley was in advanced talks with Derby's administrators Quantuma and preparing a formal offer of 50 million pounds ($68.31 million) to buy the club.