The North Sea Transition Authority (NSTA) has warned operators could be fined if they continue to delay the decommissioning of oil and gas wells.
The NSTA says there is a backlog of more than 500 wells to be plugged, and North Sea operators are "running out of time" to tackle the issue.
The BBC reports the estimated cost of £41billion is shared between the private sector and the taxpayer, but that further delays would case the cost to soar by a further £4billion.
Offshore Energies UK (OEUK) said the oil and gas sector remained committed to decommissioning but that "policy instability" had created uncertainty.
However NSTA began an investigation after identifying hundreds of wells which had missed their deadlines to be plugged, a responsibility which falls on the operator after a well comes to the end of its life.
The NSTA has cautioned that further delays risk operators and supply chain vessels moving out of the North Sea to seek other opportunities, creating additional costs.
Pauline Innes, NSTA director of supply chain and decommissioning, said: "The stark reality is that operators are running out of time to get to grips with the backlog as more contractors consider taking their rigs abroad, which damages the supply chain's ability to meet demand and remain cost competitive."
She said NSTA was prepared to help operators when necessary but would "get tough" on those who continually delay.
The NSTA says there could be more than 1,000 further wells due for decommissioning by 2030, exacerbating the backlog if it is not addressed quickly.
Read the full story on the BBC website.