Postal workers have delivered a giant postcard to Royal Mail's headquarters in protest at the company's plans to change their occupational pensions.
The Communication Workers Union is campaigning against the pension changes, as well as other issues linked to the controversial privatisation of the postal group.
The union is threatening to hold a strike ballot before the end of September unless there is a deal on pensions, pay and jobs.
"The protest is aimed at highlighting the hypocrisy of the senior executives," said the union's London regional secretary Jim Kirwan.
"The postcard explicitly names and shames those at top level management who are in line to receive enormous pensions compared to that of our members - but while they're cutting ours, they're making sure to protect their own.
"We are telling them loud and clear - hands off our pensions."
A Royal Mail spokesman said: "The member consultation is still under way. We have encouraged colleagues to contact us with their views during this time.
"After the consultation closes, Royal Mail will consider the views of members, before holding discussions with its unions, CWU and Unite. It will communicate the outcome of the consultation to plan members in due course.
"We believe that our proposal is in the best interests of plan members. Our proposal could allow us, unlike other companies, to commit to keeping the plan open to existing members for five years, subject to certain conditions, with no changes to members' benefits, retirement age or accrual rates. During that period, the proposal would also ensure that the plan could remain fully-funded. This would not be the case if no changes are made.
"If we can reach agreement on our proposal, then the commitment we propose to give would be legally binding, even if the company is under new ownership. We do not believe that there is any other UK employer whose defined benefit pension scheme members enjoy that kind of protection."
The company said none of the current executive directors were members of the Royal Mail Senior Executive Pension Plan, or any other Royal Mail defined benefit pension plan.
"The remuneration committee believes that the pension provision for executive directors provides appropriate levels of retirement benefits as part of a remuneration package that is benchmarked against comparable companies."