Haart is calling on the Chancellor to overturn the “negative” Stamp Duty hikes introduced by George Osborne after seeing house sales stumble in December.

Haart says September sales were down 18.9% year on year, and 2.9% down on August.

CEO Paul Smith said that the Stamp Duty hikes affecting those at the top end of the market as well as buy-to-let investors were damaging the market.

Smith said the measures needed to be eased “in order to increase fluidity within the market as these charges are without doubt causing a log-jam”.

According to haart’s own data, the average UK house price (measured at exchange) stood at £226,229 in September, down 1.1% from August.

In London, the average house price was 0.7% down on August at £518,997.

Smith said the housing market is “marked by a number of negatives, as prices and transactions continue to fall”.

Haart also said that while new buyer demand rose 1.5% between August and September, it was down by 22.4% on an annual basis.

The number of properties coming to the market fell 2.8% on the month and by 2.3% annually.

The firm is predicting that nationwide there will have been 49,357 exchanges overall in September.

• Separately, haart has taken on three experienced senior managers who were formerly with Countrywide. Haart’s new regional partners are James Dowling, Jason Carlisle, and Matthew Jenvey. Haart managing director Russell Jervis said: “We are lucky to have them join our ranks and look forward to working with them for many years to come.”