Would-be buyers in prime central London have opted for lavish rentals amid the uncertainty in the city’s sales market, according to a new report.

The number of new tenants paying £5,000 (US$6,576) or more per week, increased 5% in the year to August compared to the previous 12 months, according to the report Monday from Knight Frank.

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The economic and political uncertainty driving a slowdown in the general London sales market has pushed high-net-worth individuals to rent while they wait out the volatility—a trend luxury brokers have noted for several years. Final Brexit negotiations over the next few months will continue to weigh on the city's housing market in the short-term.

"Political uncertainty has made some people slightly apprehensive about the next six months," said Tom Smith, head of super-prime lettings at Knight Frank, in the report.

London’s Kensington neighborhood saw the greatest share of luxury rental activity in the first eight months of the year, accounting for roughly 17% of the city’s lettings over £5,000 per week. It was followed by neighboring Mayfair and Knightsbridge.

At the highest end, however, there are signs that high-net-worth individuals are slowly returning to the sales market.

The number of new lettings priced over £8,000 per week fell in the first eight months compared to the 12 months prior. There were only 17 such deals in the year to August, compared with 26 during the same period last year, and 27 in the first eight months of 2016.

"Demand above £8,000 per week tends to be more discretionary, and we have seen the number of deals dip this year," Mr. Smith said.

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On the flip side, the sales market is also starting to attract super-prime landlords, who are willing to sell their luxury rentals for the right price, Mr. Smith said.

"The owners of around a third of super-prime properties currently on the rental market would consider a sale at the right price. This is a higher proportion than we have seen for several years," Mr. Smith said.