In an attempt to protect these urban havens from the threat of builders, MPs yesterday urged ministers to change the law, warning that allotment sites are being swallowed up by development.
A report, published yesterday by the Environment, Transport and Regional Affairs Select Committee, also stressed the need for local councils to recognise and exploit the "therapeutic potential" of allotments for people with physical or mental health problems.
Andrew Bennett, a Labour MP and chairman of the environment sub-committee, said that the patchy nature of local council policy and an absence of credible checks on sales meant that allotments were being sold off "at an alarming rate". He added: "We have a real opportunity now - if we can tap into the latent demand for allotments which exists then we can halt the ongoing decline of allotments."
Mr Bennett's committee launched an inquiry into the issue last year after noticing a decline in allotment provision.
The report, entitled "The Future for Allotments", said there were 250,000 allotment-holders in England and Wales, with many of them getting direct benefit from having affordable fresh vegetables and physical activity.
The MPs have concluded that allotments give "undisputed health benefits".
Kay Wagland, who works for the Environment Trust, a charity based in London's East End, believes that sites such as Cable Street Community Gardens need further protection from development.
It is not hard to see why. Surrounded by council blocks and with the Docklands Light Railway running overhead, its colourful, patchwork, landscape provides a welcome contrast to the mass of surrounding concrete. "It's an outlet for people and it gives them a sense of ownership," she said. "It's a great shame when people want to start developing allotment sites like these. These areas should be cherished but there is an idea that you can develop parts of it and then give them other land elsewhere. This should be challenged."
Allotment-holder Monir Uddin said: "It's a wonderful thing. It's an excellent opportunity for youngsters to see how things grow. A lot of people in the city never get the chance to see nature at work."
James Athanaze and his wife Magdalene, who have tended an allotment in Cable Gardens for five years, also take great pleasure from their hobby. Both now retired, they tend the allotment almost every day, growing vegetables which they give to family and friends.
Mr Athanaze, 66, said yesterday: "We are devoted to our garden. It's such a relaxing place to be. The only time we don't come is on Sunday which is a day for rest. I'm worried developers may take it over. It would be a shame."
His fears are shared by MPs on the Commons committee who have concluded that there is a need for urgent action to protect existing sites. The number of plots had been falling since the Second World War figure of 1.4 million and has halved in the last 30 years.
MPs said that legislation had to be overhauled and called on the Government to issue a Green Paper "as soon as is practicable", to commission research and develop legislation. "The Government should aim to introduce the resulting Bill within the lifetime of this Parliament," the committee said.
The committee ticked off officials at the Department of the Environment, Transport and the Regions (DETR) for failing to refer requests for the sale of statutory allotment sites to the relevant minister. And MPs disagreed with DETR minister Angela Eagle's claim that allotments were essentially a local matter. "We believe that the provision of allotments is a national issue," the committee concluded.
The Royal Town Planning Institute said yesterday that allotments were a vital part of the urban framework and no further powers should be introduced to control their use.
Institute president Trevor Roberts said: "Allotments are a little bit of the countryside in the town. To town dwellers, they represent a piece of green belt on their doorstep. It therefore follows that allotments need to be protected from development pressures as much as the countryside."