Royal Mail managers have voted overwhelmingly against the Government's controversial plans to privatise the postal organisation.
The Unite union said its members who work in branches, mail centres and other offices, voted by 71% against the sell-off.
In a separate ballot of managers in the Royal Mail and the Post Office, proposals on pensions were also heavily rejected.
Unite said the pension proposals could see the annual pension cut by £3,788 for a Royal Mail manager retiring at 65 after 35 years service, from £23,099 to £19,311.
Post Office managers voted by 89% to reject proposals which Unite said could mean an employee on £15,000 a year seeing their pension reduced by £544, from £9,143 to £8,599.
Turnout in the pension ballot was 49.7%, while in the privatisation vote it was 50.7%.
Unite officer Brian Scott said the turnouts in both ballots were good, reflecting "strong opposition" to privatisation and the pension proposals.
He added: " Members have made it clear that the proposals put forward by the Post Office and Royal Mail to make changes to their pension arrangements are unacceptable.
"Our members have paid for their pensions during their working lives and it's immoral that their retirement income should be reduced in this arbitrary fashion. The respective managements should withdraw the proposals as they currently stand.
"Unite has a long-standing policy of opposition to the privatisation of Royal Mail, which is backed up by the public who don't want a national institution sold off to companies more interested in profits than providing a joined-up national service."
The Communication Workers Union is also in dispute with the Royal Mail over pensions, as well as pay and jobs, and is threatening to hold a strike ballot before the end of September if there is no agreement.
Meanwhile opposition to plans to franchise or close more than 70 Crown post offices is mounting ahead of a fresh round of strikes.
Members of the Communication Workers Union will stage three separate walkouts over the bank holiday weekend, with the five-month dispute showing no sign of being resolved.
Staff across the UK will strike on Saturday, union members in Scotland will walk out on bank holiday Monday, and employees in England, Wales and Northern Ireland will take action on Tuesday August 27.
The union said the plans to close or franchise the Crown offices - the larger branches usually sited on high streets - were meeting increasing opposition across the country, with tens of thousands of people signing petitions.
The latest public meeting will be held tonight in Holywell, North Wales, where a petition has been signed by local residents and businesses.
CWU rep Jenny Windsor said: "Holywell's Crown office is popular, well used and greatly appreciated by the local community.
"The staff have decades of experience and bring a range of expert services to customers which we fear would be lost under a franchise arrangement."
A Royal Mail spokesman said: "Only around 27% of all Royal Mail managers said they did not accept the company's proposals for the Royal Mail pension plan as they stand and only around 24% opposed the Government's plans for privatisation of the business.
"We continue to have talks with Unite on a range of issues and we are committed to making progress as soon as possible."