WESTBROOK — A development company is challenging the constitutionality of Westbrook’s rent-control law, the only one of its kind in the state.

Katahdin Corp., which sells mobile homes and operates mobile home parks, plans to sue to overturn the law within 45 days, said Kevin McCarthy, an attorney and chief operating officer for Katahdin’s parent, the Liberty Group.

McCarthy said the company will raise constitutional objections in a suit contesting the Rent Justification Board’s recent rent increase of only 0.7 percent for The Hamlet, a 288-unit mobile home park in Westbrook.

Kathadin had asked for an 8 percent rent increase for owners of mobile homes in the park.

Michael D. Cooper, Westbrook’s solicitor, said he expects the City Council will vote to defend its ordinance and the rent control board created to administer it.