In a statement, the firm said that Petricca-Riding, a planning and environmental partner based in its Manchester office, joined Irwin Mitchell last October from law firm Brabners, where she was also a partner and head of planning and environment.
It added that Petricca-Riding's recent work includes "advising a large student accommodation developer in Liverpool to provide planning advice and act on the subsequent legal challenge to the grant of planning permission at both the High Court and Court of Appeal".
On the environmental side, she has "represented numerous waste clients in court and acted for a large port organisation in respect of environmental liability and damage".
Carl Dyer, previously head of Irwin Mitchell’s planning team remains a partner in the new team.
The firm said its planning and environment team now consists of nine professional staff, of whom four are partners, across the UK.
It added that the team, which sits within Irwin Mitchell’s national real estate practice, plans to expand further and is currently recruiting in Manchester and Birmingham.
Dyer said: "Claire's environmental law expertise has filled a key gap in what was our planning team’s armoury.
"I am looking forward to working with her in what promises to be a very exciting 2020, now that the election uncertainties are behind us all."
Adrian Barlow, national head of real estate at Irwin Mitchell, said: "Environmental issues are increasingly coming to the fore as property investors, lenders, developers and occupiers are putting sustainability higher up the agenda and as environmental regulation increases.
"Environmental issues are now intrinsically bound up in planning – so it makes sense to combine these two areas of expertise into one department."