Thousands of Queensland homeowners could default on post-Christmas repayments following this week's shock interest rate rise, debt consolidators have warned.

More than 50,000 households in the state are estimated to be suffering "severe" mortgage stress and Ben Paris of Debt Mediators said he expected between 5 and 10 per cent of those would default on their mortgage repayments in the next month.

He said such people were already "just keeping their heads above water", and would struggle after the Reserve Bank increased the official cash rate from 4.5 to 4.75 per cent on Tuesday.

"For those people on the margins, with between $25 to $50 spare a week and an average weekly mortgage repayment of $330, their mortgage just became unaffordable," Mr Paris said.