The head of Britain’s water regulator said Thames Water is likely to need “substantial” funds to turn itself around.

Thames, the UK’s largest water company, has held talks with regulators and government officials who have considering nationalizing the utility amid concerns over its debts of more than £13 billion ($16.5 billion).

“They’re in discussions with the shareholders” about raising equity, Ofwat Chief Executive Officer David Black told a House of Lords committee on Tuesday. “I think to make a final judgment on that we need to see their revised business plan, but we think it’s substantial.”

Black said the company will need to raise more than £1 billion as it looks toward the next cycle of investments necessary to improve infrastructure.