New licensing laws changing the way boatmen on the River Thames work have lowered standards, a committee of MPs has heard.
Ministers say the changes will bring the UK into line with EU standards
Ministers say the regulations, passed by MPs in January, are intended to bring laws in line with EU standards.
But union leaders told the House of Commons Transport Committee the new rules has "downgraded" standards.
Instead of requiring a five-year apprenticeship, anyone can now become a captain after two and a half years.
A cross-party bid to block the new rules failed in the Commons last month.
Boatmen, who will be retested every five years, can now also captain a huge barge or busy commuter vessel at 18 instead of 21.
Richard Crease of the Transport and General Workers' Union told the committee: "In the UK we have downgraded our qualifications to a lower standard than those in Europe. There has been a dumbing down of standards on the Thames."
Survivors of the Marchioness Thames tragedy when 51 people died in 1989 have also criticised the new laws.
Malcolm Williams, who lost a number of friends in the disaster said: "My first impression was that these new regulations felt like some kind of fast-tracking system and fast-tracking leads to shallow learning and shallow learning leads to mistakes."