Its report, compiled with the Centre for Economics and Business Research (Cebr), looked at how long property takes to sell in 66 major cities across the nation. And it found that the time taken before selling has increased by 12 days over the last 12 months.
Oxford was identified as the slowest city in which to sell, with an average time of 152 days, just ahead of Aberdeen on 151 days and Middlesbrough on 149 days.
While last year London topped the poll at 131 days, it has dropped down to sixth spot, even though average time to sell has increased to 138 days on average.
At the other end of the scale, vendors north of the border enjoy much faster sales, with all three of the top spots taken by Scottish cities.
Glasgow is fastest of all at 45 days, ahead of Edinburgh at 47 days and Dundee on 72 days.
Post Office pointed to the different legal system in Scotland as making a difference in sale times.
Outside of Scotland, Coventry was the fastest place in which to sell a home, with an average time of 74 days.
Birkenhead saw the biggest fall in the time taken to sell, with a fall of 19 days compared to last year, while Barnsley saw sales speed up by 15 days.
However homes in Stoke are taking a whopping 27 extra days in which to sell, while Newport has seen sale times rise 18 days.
Ross Hunter, spokesperson for Post Office Money, said that while properties were taking longer to sell, that did not mean that interest in moving up the ladder was waning.
He added: “There is political uncertainty at the moment, and the housing market can fluctuate, so it pays to be prepared.
“Whether you are a first-time seller or someone looking to sell up and downsize, it is more important than ever to understand the market in your area to ensure a smooth transaction.”
A separate study by estate agent comparison site GetAgent also looked at the time taken to sell so far in 2019, and suggested that homes were taking an average of 247 days in order to go.
It calculates the average time to sell based on the first listing online to the point the property is marked sold by the Land Registry.
It found that things were at their slowest in the City of London, with an average of 409 days, followed by Islington at 402 days and Eden in Cumbria at 401 days.
Colby Short, founder and chief executive of GetAgent, said: “It’s tough out there at the moment, and now more than ever, home sellers should approach a sale with a clear head and realistic expectations, leaving any emotional attachment behind if they are serious about shifting their property.”