LONDON — Britain’s coalition government on Thursday confirmed plans to privatize the country’s 500-year-old Royal Mail this fall, a move opposed by postal unions and condemned by the opposition as a ‘‘fire sale’’ of a lucrative state asset.
Business Secretary Vince Cable said an initial public offering of a majority stake in the postal service was scheduled for the coming weeks.
Officials say the expected stock sale will be open to members of the public as well as to larger institutional investors. The minimum investment will be set at $1,185. Plans call for 10 percent of the stock to be given to UK-based mail staff, with at least 41 percent to be sold to the public.
‘‘These measures will help ensure the long-term sustainability of the six-days-a-week, one-price-goes anywhere universal postal service,’’ Cable said, predicting a ‘‘healthy future’’ for the company.
The government said the stock sale would allow the Royal Mail to tap investment that it needs to modernize and to compete in areas such as parcel delivery — which is becoming a major source of revenue as letter volumes decline with the growing use of e-mail.
The government did not provide details about how the stock would be priced. It added that the Post Office, which runs postal counters and was split off from the Royal Mail last year, was not for sale.
Opponents of the Royal Mail’s privatization say the economic case is not compelling. Ian Murray, business spokesman for the opposition Labour Party, accused the government of a ‘‘politically motivated fire sale.’’
‘‘The Royal Mail is a much-cherished national institution,’’ he told lawmakers in the House of Commons. ‘‘The case for privatization has not been met. With recent annual profits of over 400 million pounds, we should be allowing it to flourish in the public sector.’’
The Communications Workers Union was planning to ballot workers for possible strike action. Union members fear potential job losses.