Around one in four first-time buyers are paying stamp duty as house prices have surged, analysis has found.
The HomeOwners Alliance called for an urgent review of the tax, which applies in England and Northern Ireland.
The organisation, which made its findings using provisional HM Revenue and Customs (HMRC) figures, said around 26% of first-time buyer transactions were liable for stamp duty in the first quarter of this year.
This compares with around one in five (20%) first-time buyer transactions in the fourth quarter of 2017.
After changes introduced from November 2017, first-time buyers paying £300,000 or less for a residential property pay no stamp duty land tax (SDLT).
First-time buyers paying between £300,000 and £500,000 pay SDLT at 5% on the amount of the purchase price in excess of £300,000, while those buying a property for more than £500,000 pay SDLT at the normal rates.
Soaring house prices are pulling homebuyers generally into higher stamp duty brackets, the HomeOwners Alliance said.
Average house prices have jumped to a string of record highs in recent months, and Bank of England base rate increases have also seen mortgage rates rise, pushing up borrowing costs.
Paula Higgins, chief executive of the HomeOwners Alliance, a property advice website, said: “It’s clear that the stamp duty tax needs to be reviewed to ensure it’s facilitating rather than fettering first-time buyers.”
The Government recently announced a string of initiatives to support people aspiring to get on to the property ladder.
Ms Higgins added: “Alongside announcing new initiatives to increase homeownership, the Government needs to increase the existing first-time buyer relief threshold.
“The relief was introduced in 2017 to reduce the upfront costs for first-time buyers.
“Fast forward five years and there is a real risk first-time buyers become a taxation cash cow, which can’t be right.”
The Alliance said first-time buyer relief should be raised from £300,000 to £350,000 “as a minimum”.
It said stamp duty thresholds should also be raised annually in line with house prices.
The HomeOwners Alliance said it would like the Government “to be bold” and scrap stamp duty entirely for people buying a home to live in.
Scotland and Wales have different property taxes which apply to housing transactions.
A Treasury spokesperson said: “We want to help as many people as possible get onto the housing ladder, which is why we cut stamp duty for 90% of first-time buyers who pay it via first-time buyers relief, as well as investing £10 billion to help unlock over one million new homes.
“We keep all taxes under review.”