Central London values are now almost 16% below peaks seen in 2014 and no growth is forecast in the area before 2020.
However, there are signs that losses could be bottoming out, as the rate of price falls have slowed, Savills said.
By 2022, the agent predicts prices will have bounced back up by more than 20%
The biggest price falls of more than 4% in 2017 were in South West London, including the area from Battersea to Barnes and Richmond, in 2017 .
Values in the family-orientated parts of the capital are expected to keep on tumbling in 2018, Savills said in an update.
Buyers limited by Brexit and mortgage lending rules
Buyers in the area are constrained by mortgage lending criteria, and Brexit is also creating worries for job and financial stability, according to the agent.
Savill’s head of residential research, Lucian Cook said: “The prime central London market may be bottoming out, but we don’t expect a return to growth until there’s greater clarity regarding the Brexit process.
“A backdrop of political and economic uncertainty means the market will remain highly discretionary, while the high tax environment means that even international buyers remain reluctant to take advantage of the currency play.
“Our forecasts anticipate it will be two years before we see a bounce in values.”
“We expect continued weakness in price performance in key outer prime London markets, and are forecasting small falls next year.
“These markets are much more dependent on domestic wealth generation and access to borrowing than prime central London.
“As such, our forecasts are for much more modest house price growth over the next five years.”
