Panic-selling investors have paid more in capital gains tax since Labour came to power than any comparable period, official figures show.
The unpopular levy generated over £1bn for the Government between July and November - £200m more than in the same period last year, according to HM Revenue and Customs.
Experts said the trend was fuelled by "indiscriminate panic" and "uncertainty" among wealthy investors over Labour's intentions.
Capital gains tax is a charge on the profit someone makes when selling an asset, such as shares or second homes. The rate for higher earners is now 24pc across the board after Chancellor Rachel Reeves hiked it during her tax-grabbing maiden Budget.
But rumours ahead of the October 30 event suggested it could be increased in-line with income tax. Ministers faced criticism for failing to quash speculation before the Budget.
Since Labour's landslide win in July, investors have paid just over £1bn in capital gains tax, compared to £838m during the same period last year.
Ian Cook, of Quilter, said: "It was panic-selling because many feared that capital gains tax would align with income tax, instead of the 24pc it landed on.
"Lots of people saw the opportunity to take gains at rates they thought they were unlikely to see again in this Parliament.
"The communications from the Government were not clear and it felt potentially everything was up for grabs. I was inundated with call after call after call about pensions and capital gains tax. The panic was indiscriminate.
"I think it has a negative psychological impact on clients and investors not knowing what to do for the best."
Chris Etherington, of accountancy firm RSM, said landlords were particularly hard hit.
He said: "Ahead of the Budget, there was a lot of noise around there being a capital gains tax rate increase. Landlords in particular thought they might be first in line in terms of who might be impacted.
"There were some concerns for people that there might be changes soon after the election was announced, so people were incentivised by uncertainty to accelerate a sale.
"Over the last five to 10 years, it's been increasingly hard for landlords in terms of just running the business and the tax treatment is more penal. Many might be thinking it's time to leave the market because the Government is pointing them towards the exit door."
HMRC was approached for comment.