Any partial sell-off would involve the Post Office's 190,000 employees being offered a substantial proportion of the shares to be sold, Whitehall officials stressed.
A detailed review, setting out options for the structure and financing of the organisation will be published in the autumn, the President of the Board of Trade, Margaret Beckett, told MPs.
Other options include converting the Post Office into a public sector trust or an independent, publicly owned corporation.
Under either of these options the Post Office would remain within the public sector borrowing requirement, the Department of Trade and Industry said.
The Post Office, now chaired by Neville Bain, will also continue to have an external financing limit for at least the current year.
Under its EFL, the organisation will contribute pounds 335m to the Exchequer this year - more than pounds 1m each working day.
As a first step, Mrs Beckett said that the Post Office would be given more commercial freedom to enter joint ventures with the private sector.
In a written parliamentary reply, she said that the review would take account of the increased competition the Post Office was facing from rival operators and overseas postal services and how best private sector partnerships could be achieved.
John Roberts, the chief executive of the Post Office, welcomed the announcement.
But he stressed that commercial freedom had to be real and said urgent changes were needed to its current financial structure, which inflated prices and restricted investment.
A 49 per cent share sale could raise up to pounds 2bn for the Exchequer but would be regarded in some quarters as opening the door to eventual full privatisation of the Post Office.Reuse content