Residents invited to draw up plans for a new community centre, believe the council has set them up to fail.
The Cedars Hall building in Chicheley Road, Harrow Weald, was going to be demolished and replaced with emergency accommodation for homeless people until a public outcry forced the council to change its plans in September last year.
One of the options Harrow Council is looking at is to sell the site for development, but it has also invited Weald Tenants' and Residents' Association (TRA) to put forward proposals by the end of July.
The organisation is now drawing up plans for a community centre to be built on the site but believe the timescale is unrealistic.
Members say they do not have the funds or expertise to submit viable plans in that time. Lee Choules, vice-chairman of the Weald TRA, said: "It seems the council is planning for us to fail. It is unrealistic that the council expect us to move forward with no financial help or resources.
"The problem is having people to take it forward. We have a consultancy firm helping us, but they can't do it all as they are helping us for free."
The charity Kids Can Achieve, which supports young people in Pinner Green, has contacted the association as it wants to be part of drawing up plans - or come up with its own.
"But the residents' association says there will not be time for this.
Harrow Weald councillor Paul Scott (Liberal Democrat) said: "The deadlines are unrealistic. People asked about an extension but this was not even taken into account.
"The Weald TRA has never claimed to represent all the people who have an interest in Cedars Hall.
"This is not an attack on the residents' association, but there are people who live in Birch Park, Headstone and Uxbridge who are not members of the association."
Resident Frances Pickersgill, of Birch Park, near Cedars Hall, said: "The council are pushing a deliberate ploy to sell off the land.
"The timescale and plan would cost so much money and it has no chance of working."
Andrew Trehern, corporate director of community and environment at the council, said: "We have listened to what the residents have said and have responded to this.
"They will need to come back to us with a sustainable business plan within an agreed time scale and an assurance that they will be able to secure funding for the project."
The Cedars Hall site is worth an estimated £1.25m and the Weald TRA has until June 30 to submit a full proposal and until July 31 to come up with a business plan.