Mr Kerin was previously a partner at Grope Hamilton Lawyers, before which he spent almost 30 years at Johnson Withers.

Mr Kerin has also been active in the Australian Lawyers Alliance, serving as national president from 2012 to 2013. He now holds the position of South Australian director.

“I’m very much looking forward to joining a firm with a proud history of looking after the rights of injured people and ensuring they receive all they are entitled to under the law,” Mr Kerin said.

Maurice Blackburn CEO Greg Tucker said the firm was thrilled to have Mr Kerin on board, citing his "deep understanding of the legal landscape in South Australia".

He described expanding to Adelaide as a logical step, given that the firm had already worked with "hundreds of South Australians who have suffered injuries".

The firm is also opening a second office in Perth, which will be headed by current WA managing principal Phil Gleeson.

Mr Tucker said rapid growth in client and lawyer numbers had prompted the need to expand.

According to figures from Maurice Blackburn, staffing levels rose by 33 per cent from 2011 to March 2015.

"Our growth strategy centres firmly on investing in human capital, not via acquisitions or takeovers," Mr Tucker said.

"The performance of existing offices has been outstanding and we have moved into new premises or expanded existing ones in a number of places including Perth, Geelong, Rockhampton and Sunshine."

The firm now employs a total of 854 people, with 42 principals nationwide spread across 29 permanent and 26 visiting offices, according to Mr Tucker.