Saying he would like to challenge parks managers, London Parks & Green Spaces Forum director Tony Leach said: "What about experimenting with community gardens within existing parks?
"It would mean using a corner or a part of the park for growing food, and making them accessible, not closed off like traditional allotments."
He added: "The negative side of parks is that they are underused and people don't feel safe in them. But if they were used for growing food the footfall would increase and it would get people engaged, so the positives would outweigh the negatives."
Leach was speaking at this week's Growing Food for London conference, where park managers, community groups, growers, academics and architects met to promote urban agriculture.
Ben Reynolds, from conference organiser Sustain - the alliance for better food and farming - said: "Set against rising food prices and increasing pressures to tackle climate change, London seriously needs to consider putting aside more space for growing food."
Leach and Reynolds visited the US earlier this year to examine urban food growing projects with Royal Parks deputy chief executive Colin Buttery and Catherine Miller from the Federation of City Farms & Community Gardens.
The group produced the report Edible Cities, which recommends undertaking food-growing and training projects in parks, space around derelict council property and social housing.
Buttery said the St James's Park Dig for Victory exhibit is being used "to provoke debate and demonstrate best practice".
Making an impromptu appearance at the conference, London mayor Boris Johnson said: "I'm so excited to hear what you are discussing today.
"In my view, the number of allotments we should have here in London is ... a lot. We can use this as an opportunity to get more young people trained and employed. You have me behind you."
Parks consultant Sid Sullivan said all larger parks should have five to 12 allotments on them sponsored by growers.
He said: "All new parkland should have to have a proportion devoted to allotments to emphasise parks' green credentials and get families back into parks. This is perfectly possible. If St James's Park can have an allotment site, how can the rest of us resist?"