The group said the cash would provide "standby liquidity" during the coronavirus crisis should it be required, and stressed it was currently unused.
It comes in addition to an existing £100 million credit facility Dart has already fully drawn down.
Executive chairman Philip Meeson said: "The group is grateful to both the Bank of England and HM Treasury for the provision of the CCFF.
"Together with the fully drawn revolving credit facility of £100 million, these two sources of additional liquidity will provide the group with headroom to deal with the present disruption and associated working capital requirements."
