Cardiff Bay has been transformed into a popular area for socialising
Cardiff Bay could become a "slum of the future" because of overdevelopment, a leading academic has warned.
The building of large numbers of flats in the area with poor planning of vital amenities was to blame, said Urban Design Professor John Punter.
Lorraine Barrett AM added there was lack of community in the area which could lead to a "ghost town feel".
But leader of Cardiff Council Rodney Berman said sustainable communities were being created.
Prof Punter from Cardiff University told the BBC's Politics Show: "There are an enormous number of apartments in the Bay at the moment which are unlet and unoccupied.
"We know we've been building something like 1,250 apartments a year. I would suggest that probably one third to one half of those are unoccupied.
"I think some of them could be the slums of the future, especially the ones which are more remote, more poorly designed."
Rodney Berman explains why so many flats have been built and are planned
He said the empty properties worked against a sense of community and added that amenities vital to any built up area had not been properly planned, with people having to commute to access services.
He also criticised that much of the accommodation was not affordable housing and was not ideal to families, despite 4,500 families in Cardiff being on housing waiting lists.
Lorraine Barrett AM agreed with his findings.
She said: "I've got real concerns about no community being built up over the years and I think that can bring with it that sort of ghost town sort of feel."
It is feared the value and condition of the unoccupied flats will decline and the absence of amenities and sense of community will lead to the area becoming a place where social problems do proliferate.
There are worries flats will remain empty
Ms Barrett said: "I'm concerned that when you've got empty properties, the landlords may well just rent them out to a wide range of people who may not be suited to that type of living.
"I think we could be storing up some social problems for the future."
Cardiff Bay has seen massive investment over the last decade with the area being transformed from an industrial docklands landscape into a cosmopolitan tourist area with numerous bars and restaurants.
The Welsh assembly building and Wales Millennium Centre have recently opened in the area and the International Sports Village which is under construction.
Along with it, thousands of apartments have been built.
But in recent months, falling property values in the area have become problematic with some reporting difficulty in selling or sustaining huge losses.
But some developers remain confident that, once current economic gloom lifts, Cardiff Bay will grow and prosper.
Cardiff Council leader Cllr Rodney Berman said the creation of new apartments on brown field sites was developing sustainable communities with apartments being built close to supermarkets and retail parks.
"The argument we are not creating sustainable communities is not borne out," he said.
"We are taking great strides, we've got tough new guidance and we are looking more and more at developers contributing towards community facilities and not just building apartment blocks in isolation so we are creating truly sustainable communities."
He added: "If you can put a concentration of what you are building in the future on brown field land you can build more sustainable communities where you can have flats and apartments close to the facilities."
The Politics Show for Wales is shown on Sunday 1200BST on BBC One.
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