Five more refusenik water companies could also be forced to reveal details on the discharge of raw sewage after a ruling by the information watchdog including South West Water.

Adam Vaughan www.thetimes.co.uk

The data watchdog has ordered a water company to release secret figures that could reveal illegal sewage spills, paving the way for five other firms to be forced to do the same.

In a victory for The Times’s Clean it Up campaign, the Information Commissioner’s Office (ICO) ruled that United Utilities must share data showing the start and stop times of raw sewage discharges in 2022.

Cross-referenced with weather data, the information could reveal evidence of “dry spills”, the illegal practice of releasing raw sewage into rivers and seas when there has been no heavy rainfall.

Dry spilling is more environmentally damaging because there is no rain water to dilute the pollution and river levels might be lower on dry days. It could put swimmers at risk too, since they are more likely to go in on dry days, which are usually considered safer.

A lawyer at one of the six firms refusing to share the data — Anglian Water, Northumbrian Water, Severn Trent Water, South West Water, United Utilities and Yorkshire Water — had argued that it was so complex that “it is the regulators and not the press or the public” that should see it.

Several of the companies argued that their secrecy was justified because releasing the information would prejudice a joint investigation by the Environment Agency and Ofwat, the water industry regulator.

However, the ICO has ruled against United Utilities. Given that the times and locations of sewage spills was “purely factual information”, the data watchdog said it was “struggling” to see how its publication could obstruct the investigation.

David Black, the chief executive of Ofwat, had publicly said his investigation was not a reason to keep the figures secret, the ICO noted. Moreover, it said there was no evidence the water firm had asked the regulators if sharing the information would prejudice their investigation.

Another reason for ordering the data be made public was a recent appeal tribunal ruling in favour of Steve Lavelle, a campaigner who sought data from Northumbrian Water on sewage dumping in the sea at Whitburn, South Tyneside.

In light of that case and the failure of United Utilities to explain how the regulators’ investigation would be affected, the watchdog demanded it publish the data within 35 days. “It’s not in dispute that dry spillages have occurred,” the watchdog said. “The start and stop times won’t give any indication of how these dry spills will be considered by either regulator or what action might be taken as a result of the investigations.”

United Utilities, which serves the northwest of England including Liverpool, Manchester and the Lake District, claimed that releasing the data would amount to “inappropriate sharing of information”. It also warned it could lead to “misinterpretation” and was “disproportionate” to share the figures for its 2,000-plus sewage outfalls.

James Wallace, head of the charity River Action, said: “When someone deliberately withholds information, it is usually because they have something to hide. Bearing in mind the risk to rivers of ecological collapse and spread of infectious diseases to humans by the release of untreated sewage, the ICO ruling on water companies sharing raw sewage discharge data is essential.”

The data watchdog has issued a decision against only United Utilities, which twice refused to release the figures to The Times. However, because it dismantled the same argument used by the five other water companies, similar decisions are expected against them imminently, forcing them to release the data.

The companies could choose to appeal in a final attempt to keep the information secret.

A United Utilities spokeswoman said: “We note the ICO’s decision notice and we are considering our next steps.”

An Environment Agency spokesperson said: “As a regulator, we aim to be transparent and evidence-based; we expect the water industry to do the same.”

The Times is demanding faster action to improve the country’s waterways. Find out more about the Clean It Up campaign.