Thousands of Britons with holiday homes in Portugal face losing their properties under a new law introduced by the Portuguese government.

The law, re-introduced from similar 2005 legislation, requires owners of waterfront or riverside properties to prove their building has been under private ownership for the last 150 years.

If a property is within 50m of the coast, or within 30m of rivers or lakes, it will be affected by the law, which applies to both local and overseas owners.

There is deep concern over the law, since locating documents proving ownership over the preceding 150 years is a difficult if not impossible task.

There was a glimmer of hope last month, however, as affected residents lobbied the government to change the law, resulting in it being limited to buildings constructed after 1951. It also scrapped a proposed deadline of July 1, by which date documents had been required to be sent in.

But the government reserves the right to use the legislation at any time, although it is most likely to be used when a property is sold on. This may have the effect of reducing the number of waterside properties for sale, since owners may be fearful of not being able to prove ownership –and therefore face extra taxes, financial penalties or even have their land reclaimed.

Are you one of our holiday home insurance customers affected by this law? If so, tell us your story below.