A woman whose son was killed in the Marchioness disaster has attacked plans for less experienced boat masters to be allowed on the River Thames.
Margaret Lockwood-Craft says the plans must be scrapped
Margaret Lockwood-Croft wants the government to scrap plans to halve the amount of experience required, saying it would result in another tragedy.
Earlier, she joined members of the RMT union in a protest on the river.
Her son Shaun was among 51 people killed when the Marchioness pleasure boat collided with a dredger in 1989.
Strict measures governing licences to work on the Thames were put in place after the tragedy.
The government is considering responses to a consultation on the issue, but has pledged that safety will not suffer.
Mrs Lockwood-Croft said: "Unless these plans are stopped there will be another Marchioness-type tragedy on the Thames.
"These waters are highly dangerous, and proper training of staff is needed."
Travelling on a passenger vessel for the first time since the disaster, she joined officials from the RMT and other craft in blowing whistles as they sailed past the House of Commons on Tuesday.
A licence to work on the Thames currently demands five years' experience on the river and four examinations - which watermen say is necessary to be able to handle different crafts in different tidal and weather conditions.
Under the proposed changes a boat master would need two years' experience and the period for qualifying service to gain local knowledge would be reduced from two years to six months.
Bob Crow, the RMT general secretary, said: "It is even proposed to do away with the current mandatory college-based training to reduce the qualifying age for a licence from 21 to 18 years for cargo vessels up to 40m long."
A report from the Maritime and Coastguard Agency last year found safety aboard Thames riverboats had reached acceptable levels.