Irwin Mitchell’s profit before tax has fallen by more than 25 per cent, from £16.7m to £12.4m last year.

The results are the first to be announced since the firm carried out its largest merger to date by acquiring Thomas Eggar in November.

The merger gifted Irwin Mitchell its first major base in the south east outside of London and boosted its private wealth practice.

Irwin Mitchell chief executive Andrew Tucker attributed the fall in profits to the firm’s investment in the merger.

Tucker said: “There are many reasons for real confidence in our business, despite the reduction in profit this year. That is a short term issue driven by the significant investment in the merger to ensure it was a success.

“The board is comfortable that sacrificing profit in the short term will deliver greater benefits to the business in the medium term as we reap the return on investment.”

He added that Irwin Mitchell had decided to “fast track” the integration of teams and IT systems from Thomas Eggar to the wider group.

Despite the fall in profit Irwin Mitchell’s turnover increased by 8.2 per cent, from £204.m in 2014/15 to £221.3m last year.

Irwin Mitchell saw the departure of five partners from its London real estate practice to Dentons last week, including London real estate head Rob Thompson.

The team also included partners Robert Dowdell, Lewis Myers and head of corporate real estate Jayne Schnider. The team largely focuses on real estate development and investment work and advises a number of clients including Prestbury, Max Property Group, and Raven Russia.

Dentons later picked up Irwin Mitchell real estate finance partner Simon Tweedle. All of the partners, with the exception of Schnider, joined Irwin Mitchell in 2010 from legacy firm SJ Berwin.