Nearly 30 per cent of tied tenants have debts of more than £50,000 according to new research.
The Pub Revolution branch of trade union GMB commissioned an independent survey of its 3,500 members, and of the 3,000 that responded, 29.2 per cent said they had debts of more than £50,000.
In total, 80 per cent of tied tenants said they had debts of £10,000 or more.
Meanwhile three quarters (73.3 per cent) of respondents said their income - after rent and other costs was below £10,000. Only 2.5 per cent take home more than £35,000.
The survey also revealed that 87 per cent of tied tenants asked do not think that their current rent is "fair, maintainable or achievable" and 82 per cent said the way their rent is calculated needs to change.
A similar number (87 per cent) also stated that they believe the business opportunity available at their pub was misrepresented by the pubco.
GMB national officer Paul Maloney described the findings as "frightening".
He said: "I was genuinely quite shocked by the results of the survey.
"Whatever happens now the industry, and particularly the captains of the industry, need to listen and take on board the concerns."
However the British Beer & Pub Association (BBPA) raised questions about the findings of the survey.
A spokesman said: "The GMB's finding that 73 per cent of licensees have an average disposable income of £10,000 or below a year, compares with the fact that the average family in Britain has a disposable income of £7,400 a year.
"Likewise, average household debt in the UK is over £58,000, compares with the GMB's finding that 29 per cent of licensees have debts of £50,000 or above, while 69 per cent of licensees have debts below £40,000. Everyone recognises the recession has bitten hard and reduced incomes significantly. Equally, we are determined to work in partnership to make pubs and publicans more prosperous."