In an interview with Third Sector, he said that the business plan had now been revised, the aims of Heyday remained valid and he thought it could succeed at the next stage.
He compared Heyday to previous Age Concern projects and said the revision "doesn't feel, in essence, that uncomfortable a process to me. If you look at our track record on these things, it is actually pretty good at getting them right, but getting them right involves having enough flexibility to change when you need to try different routes to making it work."
Heyday, launched last May, is a membership organisation for people who are nearing retirement. It aimed to recruit 300,000 members in a year but so far has 45,000, 31,000 of them transferred from another organisation.
Tony Page, managing director of Age Concern Enterprises (Acent), resigned over Heyday, but terms relating to his departure are protected by a confidentiality agreement. Des LeGrys, chair of Acent, and Norman Biddle, chair of Age Concern Enterprises Holdings, have also resigned. At least 33 Heyday staff are to be made redundant.
Asked if it was correct that £10m had been put into Heyday, Lishman said £5m of the charity's reserves had been used, but declined to give more details. "£10m is not a figure that I recognise," he said. Age Concern's income in 2004/05 was £75m.
Asked about an early membership target of 796,000, Lishman said that the original business plan made "very big claims indeed" and that some of the tensions and resignations were linked in part to making the figures more realistic.
The risk was assessed using research and marketing agencies, Lishman said: "You do the research; you find out if it works. Sometimes it takes off and flies; sometimes, for whatever reason, it doesn't.
"The research we did was a fair professional basis, accepted as such by the marketing agencies and others we worked with for what we were setting out to do."
Commenting on a 2004 report from one trustee saying Heyday would not work, Lishman said: "Those views simply were not reflected by the trustees as a whole."