Failure by the UK Ship Registry to boost tonnage and cadets in recent years has put the Red Ensign at risk of being dragged down into the gutter, Nautilus International assistant general secretary Ronnie Cunningham warned the 2019 Trades Union Congress in Brighton.
The government set itself the target just two years ago to double the number of ships on the UK register, but the sad reality is that tonnage under the Red Ensign actually fell by more than one third in that time.
'It doesn't stop there,' Mr Cunningham continued. 'Government and ship owners committed to increasing Merchant Navy cadet numbers by 400 per year but have fallen short of this with only 50 being taken on in the last 12 months.'
That is a mere 12.5% of the additional cadets promised.
'The government's own statistics show that UK seafarer numbers have fallen by almost 8% over the past 15 years,' Mr Cunningham said.
He warned that there was a very real risk that the Red Ensign will be dragged down into the gutter and called on delegates at the conference to remember those workers who deliver 95% of everything and yet are so often out of sight and out of mind.
Mr Cunningham said ministers rarely talk about the way that trade will actually be moved, or the countries involved in keeping the UK supplied.
'The government has forgotten that 95% of trade comes and goes by sea. I have lost count of the number of times government minister have told us we will "trade our way" out of the downturn or that trade deals will be our salvation in a post-Brexit economy.
'It is a sad reality that the proportion of trade being carried on UK ships, flying the UK flag and crewed by UK seafarers is declining,' he added.
The motion was supported by rating and RMT member Karlson Lingwood who called for a fair playing field in the UK maritime sector and for there to be a real link between the Red Ensign and employment opportunities for UK seafarers.
Mr Lingwood told the Congress that next year would be 100 years since the US introduced the Jones Act to protect the US maritime industry and called forth UK to consider similar protection for British shipping and British seafarers.