Opening up the postal market to competition has seen "no significant benefit" for consumers and businesses, an independent report has found.
The findings are part of a review of the UK postal sector commissioned by the government, whose full report is due this summer.
Today's report found that the liberalisation had led to a "substantial threat" to the financial stability of the Royal Mail and the universal service.
In 2006 other operators were allowed to collect and deliver mail, ending the Royal Mail's 350-year monopoly.
As a result of the changes, the independent review said that the "status quo is not tenable".
"The policies needed to establish a sustainable future will be the focus of our report later this year," the BBC quotes the report as saying.
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