The government has been accused of trying to hide a lack of action over the dumping of sewage into rivers and coastlines around England.
Ministers were told their approach to transparency "absolutely stinks" after they refused to disclose to MPs if and when they had met with water bosses to solve the problem.
It comes after the government was placed under investigation by the environment regulator for allegedly failing in its duties to manage the quality of water.
Deteriorating water quality in England’s rivers and seas is a growing concern, with private water companies routinely discharging untreated human waste on a regular basis.
Despite rules that say they should only be dumping the sewage in exceptional circumstances, official figures show storm sewage discharges surged by more than a third between 2019 and 2020, to 403,171 incidents.
England's chief medical officer Professor Chris Whitty has said the growing problem of faeces in river water is a “major issue” and “unacceptable on health grounds”.
But asked through a written parliamentary question when they had met with water companies over the issue, Conservative water minister Steve Double appeared to stonewall.
He referred MPs to another answer he had previously given in which he said the government "repeatedly made it clear to the water industry that the current use of sewage discharges is unacceptable" – but gave no list of meetings or indication that any had focused on the problem.
"This absolutely stinks of ministers hiding from their failure to stop the sewage scandals," said Liberal Democrat environment spokesperson Tim Farron, who asked the question.
"When will the Government come clean about their lack of action on water companies dumping sewage into our treasured lakes, rivers and beaches?"
Mr Farron, a former Lib Dem leader, added: "It is time we made the polluter pay for their actions.
"This should include a Sewage Tax on the multi-billion pound profits of water companies. Instead, we have a Minister refusing to even tell us if they are meeting with water companies, let alone taking tough action on them. What a complete farce.
"Both the Environment Agency and British public want action on this, yet Conservative Ministers seem to think otherwise."
The Office for Environmental Protection's investigation, launched last month, is probing whether environment secretary George Eustice, the Environment Agency (EA) and water services regulator Ofwat failed in their duties in the management of water quality.
The OEP investigation will seek “to determine whether these authorities have failed to comply with their respective duties in relation to the regulation, including the monitoring and enforcement, of water companies’ own duties to manage sewage”, the organisation said in a statement.
Approach for comment, a Defra spokesperson said: “Restoring our rivers is a government priority. We regularly meet water companies at an official and ministerial level to discuss policies and issues related to water quality.
“Ministers and water companies have held three meetings this year where storm overflows were specifically discussed, in addition to further regular meetings to discuss a range of other water quality issues over the course of the year.
“We have been consistently clear that we expect water companies to take significant and urgent action to tackle pollution and we won’t hesitate to take further action if we do not see the changes we expect. This has been communicated directly to water companies at all levels.”
