The opposition alliance, which includes the parties of former presidents Mohamed Nasheed and Maumoon Abdul Gayoom, said they had enlisted British lawyer Ben Emmerson to advise them on securing UN mediation in the crisis.
Emmerson, a UN special rapporteur until last year, is also a member of Nasheed's pro-bono international legal team, which includes high-profile rights lawyer Amal Clooney.
His appointment follows reports that President Abdulla Yameen, who declared a state of emergency in a crackdown on dissent earlier this month, had declined an offer from UN Secretary General Antonio Guterres for multi-party talks.
Yameen has stepped up a crackdown on opposition activists, including his estranged half brother and ex-president Gayoom, since imposing a draconian state of emergency on February 5.
More From This Section
Yameen's education minister Aishath Shiham on Tuesday told the UN Human Rights Council in Geneva that the Supreme Court's "judicial overreach" had threatened democracy in the Maldives.
The Council of the European Union on Monday urged Yameen to end the state of emergency, release all political prisoners and restore rule of law. It warned of sanctions if Yameen failed to comply.
"The current situation is not in accordance with the principles of democratic rule and separation of powers," the Council said.
"If the situation does not improve, the Council may therefore consider targeted measures."
It said the European Union was ready to support any UN facilitation of talks between Maldivian parties to end the standoff, which it said threatened the safety of residents and tourists visiting the popular holiday islands.