Irwin Mitchell paid £24m to acquire Thomas Eggar last year, a move that contributed to profits falling by almost 60% during 2015-16, according to the firm's latest accounts.

The limited liability partnership (LLP) accounts, filed with Companies House, show that profit available for division among members fell by 59% from £20.6m to £8.4m during the last financial year.

The accounts state: "The board took a deliberate decision to fast-track the integration of Thomas Eggar, which has led to a short-term impact on profitability in FY16 but which we view as being the right decision longer term."

The trade and assets of Thomas Eggar were acquired for £23.6m plus "acquisition costs" of £533,514 – a total value significantly lower than the £41m revenue figure posted by the southeast firm for 2014-15.

As a result of the takeover, total revenues for the Irwin Mitchell LLP grew 7.3% from £185.6m in 2014-15, to £199.2m. The firm adopted the FRS 102 financial reporting standard during the year, prompting a change to its accounting policy "in respect of valuation of unbilled time on contigent matters". As a result, accrued income has been reduced by £31.4m as of 30 April 2015, while work in progress has increased by £31.7m.

The amount due to creditors increased significantly, from £6.6m to £42.5m, driven principally by £29m in new bank loans and overdrafts.

The Thomas Eggar takeover also contributed to a 24% rise in fee earner numbers, from 1,072 to 1,205, with support staff numbers up 18% from 669 to 787. As a result, total staff costs rose 17% from £60.1m to £70.4m.

The accounts also describe the firm's mechanism for sharing profit with its partners.

The accounts say: "Individual members are awarded a base profit share at the start of the year. In addition, a minimum of 28% of the profit, after the deduction of members' base profit shares for the years, is paid onto a bonus pool that is allocated to members after the end of the financial period."

When partners are made up, they are "required to contribute capital amounting to 30% of notional salary plus any guaranteed profit share within two months of becoming a partner or as and when required by HMRC legislation".