The redundancies follow the departure of three senior figures from trading arms of Age Concern England, who were worried about the management of Heyday, including its failure to recruit enough members.
The charity also faces a partial recruitment freeze, and has offered some staff voluntary redundancy.
A spokesman said: "These steps are necessary because income from trading has been lower than expected and new trading arrangements that, over time, will help improve this situation may result in a dip in income in the short term."
Age Concern England used £5m from its trust fund to set up Heyday with corporate partner Fortis Insurance last year. It aims to help younger people plan for retirement.
It set out to gain 250,000 members by the end of this year, using local organisers to sell £20 subscriptions. But it has so far recruited only 45,000, and has decided instead to start asking employers to purchase Heyday membership for their staff.
It is this change to the recruitment process that has had the biggest impact on staffing levels. "Thirty-three Heyday staff working in London and across the UK on the recruitment of individual members are being consulted about potential redundancies in their teams," said the Age Concern spokesman.
In the planning stage, Heyday was managed by Age Concern Enterprises, which last year made more than £20m from the sale of products and services.
But before its launch last May, it was brought under the direct control of Age Concern England.
Heyday is not a registered charity, but the spokesman said: "Heyday's core purpose is charitable and our board decided its activities sit best within Age Concern England."
When concern about the management of Heyday began to surface, including poor progress with recruitment, Tony Page, chief executive of Age Concern Enterprises, resigned. He was followed by Des LeGrys, its chair, then Norman Biddle, chair of Age Concern Enterprises Holdings, another of the charity's commercial operations.
A source said that all three men had serious misgivings about the way Heyday was being run after it was taken under the control of Age Concern England. At least one raised his concerns with the Age Concern England board of trustees, said the source.
The Age Concern England spokesman declined to comment on why the three had resigned.
"Age Concern England has robust financial and governance processes and these have, quite properly, applied to Heyday," he said.
He added that the initial membership targets were ambitious. "We accept we have not met them," he said. "The new business plan reduces our operational costs in line with the membership growth we now expect.
"Age Concern England is planning to reduce its costs in the year ahead, but this is not a result of Heyday.
"Rather, we are responding to new terms of trade in our social enterprise activity, Age Concern Enterprises, which will see reduced income for us next year.
"Heyday remains one of Age Concern England's corporate priorities, and our ageing population means there will be a growing need for its services."
He said the Age Concern England finance committee and board of trustees had received full regular reports about Heyday's progress and had approved the revised business plan.