The number of homes selling for over £1 million was lower in the first half of 2017 than during the same period a year earlier, according to analysis.
While prime property sales in the North West of England and Yorkshire were up year-on-year, the number of million pound property sales in London, Scotland and Wales was down, Lloyds Bank found.
Across Britain, there was a 1% fall in the number of properties sold for more than a million pounds in the first six months of 2017 compared with the same period in 2016, with number of sales edging down from 6,684 to 6,613.
London, where sales of £1 million-plus homes tend to be concentrated, saw transactions in this bracket plunge by 7%, from from 4,230 to 3,940.
By contrast, million pound property sales in the North West of England and Yorkshire and the Humber have jumped by 55% and 45% respectively, albeit from much lower bases.
Lloyds Bank's research looked at figures from the Land Registry covering England and Wales and the Registers of Scotland.
Sarah Deaves, private banking director at Lloyds Bank, said stamp duty changes in previous years, which have made the tax more expensive for buy-to-let investors and for people purchasing top-end properties, may be partly behind the figures.
She continued: "There are several factors that could be responsible for the ongoing uncertainty in the market, including interest rates and economic stability."
Lloyds said despite a year-on-year fall in million pound property sales, the top end of the market has held up relatively well, with sales of properties for under £1 million having fallen more sharply, by 7%, across Britain in the first half of 2017 compared with the same period last year.
Here are the numbers of million pound property sales in the first half of 2017 and the percentage change compared with the first half of last year, according to Lloyds Bank:
:: North East, 13, 18%
:: North West, 132, 55%
:: Yorkshire and the Humber, 55, 45%
:: East Midlands, 24, minus 27%
:: West Midlands, 81, 33%
:: East of England, 527, minus 4%
:: London, 3,940, minus 7%
:: South East, 1,497, 15%
:: South West, 282, 5%
:: Wales, nine, minus 31%
:: Scotland, 53, minus 35%