Irwin Mitchell has appointed a new chief executive following the announcement that John Pickering is to stand down from the position, ending a 37-year career at the firm.

Pickering will leave the business after a transitional period, with former chief executive of the firm's personal legal services (PLS) division Andrew Tucker set to take up the role on Monday. Tucker was appointed by the firm's management board.

Pickering joined Irwin Mitchell in 1977 and became a partner in 1980. He headed up the firm's personal injury practice before being elected national managing partner in 2009. He became group chief executive in 2011.

Pickering said: "This has been a difficult decision for me because I am deeply committed to the firm. I believe we have created a basis for the future success of the business. The group will need a settled management team in place throughout this and, therefore, I concluded that a well managed and orderly transition to a new leader was appropriate now and the right direction for the firm to take. Andrew is the right man for that task and I am pleased the board has appointed him."

He added that he now plans to pursue non-executive director positions within other businesses.

Tucker joined Irwin Mitchell in 1985 and became a partner in 1988. He became a board member in 1999 and led the firm's personal injury division from 2009. Following a restructure of the firm in May 2011, he became chief executive of PLS and a member of both the board of Irwin Mitchell Holdings and the firm's executive board.

The management shake-up follows a period of rapid growth for Irwin Mitchell. Last month the firm secured a four-year, £60m bank loan with three major UK banks to fund its strategic growth plan.

The loan, which also includes a £30m 'accordion' option facility for further capital, was underwritten by HSBC, Lloyds Bank and the Royal Bank of Scotland, and hailed by the firm as a vote of confidence in its business plan.

Irwin Mitchell became one of the first large UK law firms to apply for an alternative business structure licence in January 2012.

In the last 18 months the firm has recruited more than 30 partner-level positions, while in 2012/13, the Irwin Mitchell group – which includes subsidiary practices and businesses tacked on after the firm secured a multiple alternative business structure license – saw revenue pass the £200m mark for the first time.