Gilbert + Tobin will merge with Perth-based firm Blakiston & Crabb in order to secure an energy and resources practice and take on the top-tier firms.
Seven partners and 24 lawyers from Blakiston & Crabb will join Gilbert + Tobin, with the firm set to benefit from Blakiston & Crabb's international work and list of clients operating in Africa.
Managing partner Danny Gilbert told Lawyers Weekly that acquiring the energy and resources expertise, as well as a Perth base, was necessary for the firm to move into a new tier of legal services.
"It's hard to think how we could really say that we were one of the leading corporate firms in the country when, if we don't have corporate expertise in this area, we miss a lot of work," he said.
While Gilbert did not rule out a global merger in the future, he dismissed speculation that his firm was only making the move into Perth to make it more attractive to global law firms.
"We're doing it because it's a sensible thing for us to do," he said.
"We're not looking to do a global merger but if the right opportunity came along with one of the truly outstanding global firms, then that would be something we'd have to think about. Having a resources practice would aid that if indeed at the time that's what we wanted to do."
The merger follows a one-year alliance between the firms. Prior to that, the firms shared little in common, with Gilbert making a "cold call" to Blakiston & Crabb's managing partner in order to start a relationship.
"I picked the phone up one day and made a cold call to Michael Blakiston. I had never met him or spoke to him before in my life," said Gilbert. "I said 'I'd like to come and talk to you. We're wondering what we should be doing in Perth'."
Gilbert + Tobin's move into Perth follows a host of local and international law firms to enter the market over the last 18 months - most notably Clifford Chance earlier this year and Allen & Overy in early 2010.
A one city firm just 18 months ago, Gilbert + Tobin initially commenced its national expansion by opening a five-partner office in Melbourne.
However, Gilbert said the firm is not on a mission to "go national", but rather, to position itself where a "law firm needs to be".
He said there are no plans for the firm to open additional offices in Brisbane or Adelaide.