More than 300,000 properties in Andalucia, many sold to unsuspecting British expats, are believed to be illegal.
They were built with planning authority issued by corrupt local councils before a recent clampdown by the regional government.
One Brtish expat couple living in Albox, Andalucia, could see their house demolished after they lost an appeal to save their Spanish property.
The couple – who have vowed to save their home – are one of a group of British-owned properties served with demolition orders in 2012.
A decree passed in January will allow for most illegal homes to be “regularised” at considerable expense to the homeowners but 10 per cent will have to be demolished, officials said.