The Government came under fresh attack over its controversial plans for the Royal Mail as Business Secretary Vince Cable confirmed it will press ahead with privatising the service.
Mr Cable said an initial public offering (IPO) is expected in the coming weeks, describing the move as "an important day" for the Royal Mail and its employees.
The announcement came ahead of a meeting of Communication Workers Union officials to discuss the sell-off and their plans for a strike ballot.
The union is planning to ballot its members for strikes over pay, jobs and other issues linked to privatisation.
Institutional investors and members of the public will be eligible to apply for the shares. Ten per cent of shares will be allocated to Royal Mail employees and the public will be able to buy a minimum of £750 worth of shares.
Mr Cable said: “The Government is taking action to secure a healthy future for the company. These measures will help ensure the long-term sustainability of the six days a week, one price goes anywhere universal postal service.
“By announcing that we intend to move ahead with a sale of shares in Royal Mail we are completing the third and final part of the reforms agreed in Parliament two years ago.”
Chuka Umunna, shadow business secretary accused Ministers of pushing forward with a politically motivated "fire sale" of Royal Mail to "fill the hole left by George Osborne's failed plan".
"This is taking place despite opposition from a huge coalition including the Conservative Bow Group, the Countryside Alliance, the National Federation of Subpostmasters (NFSP), the cross-party BIS (Department for Business, Innovation & Skills) Select Committee as well as Royal Mail employees themselves.
"The Government has not addressed the huge concerns which remain on the impact the Royal Mail sale will have on consumers, businesses and communities, but ministers are ploughing on regardless."
The National Federation of SubPostmasters (NFSP) called on the Government to safeguard the future of thousands of post offices by halting the sale.
The NFSP said a failure to protect post offices would amount to a "reckless gamble" with the future of the post office network.
General Secretary George Thomson said: "I am extremely disappointed and concerned that the Government is pressing ahead with a plan that will undoubtedly jeopardise the future of thousands of post offices.
"We simply have not had the promised new government work that needs to be delivered before the sale of Royal Mail and which would safeguard the future survival of an independent Post Office.
"We are now calling on the Government to halt the sale until we can be sure that new work is forthcoming. We are also urging ministers to retain a share in Royal Mail to ensure government has the ability to protect the interests of post offices and their customers, which are already under serious threat.
Nick Wells, chief executive of TNT Post, said privatising a monopoly was bad for consumers, business and UK plc.
"Royal Mail should be open to the pressures of competition and no longer enjoy the Government gift of a 20 per cent cost advantage over its competition", he added.
A spokesperson for the Royal Mail said: “Royal Mail and the Post Office Limited were formally separated in 2012. For the past year the two companies have operated independently of each other, strengthening their relationship and allowing each organisation to focus on its own priorities. Royal Mail and Post Office Limited signed a long term commercial agreement for the continued supply of services in 2012.
"VAT exemptions for core postal service delivery by Universal Service Obligation (USO) holders are in place in the vast majority of EU countries under European directive. Royal Mail is the USO holder in the UK, one of TNT Post UK’s significant investors, PostNL is the privatised USO holder in the Netherlands, where a similar VAT exemption applies.
"Royal Mail does not accept TNT’s calls for the removal of the exemption."
Additional reporting by Press Association