A senior Conservative MP said he swam in sewage when visiting south Wales as a child.
Ashford MP Damian Green, 67, said attitudes towards sewage spillages had changed in recent years.
Welsh Water released sewage into rivers, lakes and the sea for almost 600,000 hours last year.
England’s water companies recently pledged £10bn after apologising for “not acting quickly enough”.
“I’m not denying its a big issue but it always has been. I remember as a child in south Wales swimming in sewage.
“Jackson’s Bay in Barry used to be a sewage outlet where we all went and paddled and swam – it was regarded as acceptable,” Mr Green said on ITV’s Peston.
According to Natural Resources Wales, Jackson’s Bay’s water quality dropped from good in 2019 to sufficient in 2020, where it has remained since.
Sufficient is one above the worst ranking of poor.
Welsh Water recently said it would spend £840m by 2025, followed by a further £1.4bn between 2024-2030 on work to tackle the problem and protect the environment.
Chief executive Peter Perry said last week that he and company chief finance director Mike Davies would not be taking their bonus this year after the firms sewage figures were released.
Emma Clancy, chief executive of the Consumer Council for Water (CCW), said this could mark a “turning point in water companies taking ownership of tackling the challenges facing the sector”.
But Josh Harries of Surfers Against Sewage, an environmental charity that campaigns to protect the ocean, said it was hard to believe water companies.
“Why should we trust them? They’ve overseen decades of mismanagement of our sewerage network with our rivers and seas paying the price.
“We need more robust regulation and strict enforcement to hold these companies to account.”
The majority of sewers in Wales are “combined sewers” and carry both sewage and surface water from roofs and drains.
An overflow during heavy rain can lead to sewerage system becoming overwhelmed.