Both companies have breached their legal obligations by failing to adequately tell investors the risk climate change poses to their businesses, legal NGO ClientEarth said.

While the Financial Conduct Authority has yet to sanction a company over its climate disclosures, the latest ClientEarth complaint is the first since the UK finance minister told the FCA in March to "have regard" in its work to the government's pledge to reach net zero carbon emissions by 2050.

The complaint also follows a stinging report from auditing watchdog the Financial Reporting Council in November that found most company accounts were not factoring in climate risk properly and needed to do better.

Under UK law, a company has an obligation to disclose material risks to their business that could impact its value, so shareholders can make an informed judgement on whether to invest.

By not doing so, Just Eat and Carnival have breached several of the disclosure and listings rules set by the FCA to help markets function well, protect customers and enhance financial market integrity, the NGO said.

In the case of Just Eat, ClientEarth said the company made no reference to climate change in its 2020 financial reporting and had no strategy to reduce its carbon emissions in line with the Paris Agreement on climate.

It also gave only a limited commentary on environmental impacts and opportunities, including around its food packaging, particularly its use of plastics, and risked misleading investors over the sustainability of its business model.

A spokesperson for Just Eat said it did not recognise the allegations made by ClientEarth and had disclosed all material information to investors in its annual report.

"We are committed to reducing our carbon footprint and providing accurate information to our key stakeholders," the spokesperson said, citing an ongoing plan to carry out a carbon footprint analysis of the company.

"This is currently in progress and once we have an accurate measurement in relation to the analysis, we will be setting reduction targets and reporting these over the coming months."

Carnival, meanwhile, also made no reference to climate change in its annual report and only "vague" statements in its strategic report, with no concrete analysis of the impact of climate change on its business model, the NGO said.

Carnival did not immediately respond to requests for comment.

"Recent global efforts to phase-out fossil fuels and single-use plastics, shifts in consumer behaviour, and abrupt changes to regulatory and business environments all present very real challenges to their financial and operational health," ClientEarth lawyer Maria Petzsch said.

"These impacts are material to investors, who expect to be given the full picture."

In a complaint filed on Tuesday, the environmental law charity said it had asked the FCA to refer both companies for investigation, although the regulator is under no obligation to act.

A previous complaint to the FCA by ClientEarth over the disclosures of insurers Lancashire Holdings, Admiral and Phoenix Group in 2018 was not successful.

The NGO also said it had written to the FRC, which oversees the auditing profession, to ask them to liaise with the FCA over any action as it relates to the companies' respective auditors, Deloitte and PwC.

A spokesperson for Deloitte, PwC and the FCA declined to comment. The FRC did not immediately respond to a request for comment.

(Reporting by Simon Jessop; Editing by Anil D'Silva)

By Simon Jessop