Anerood Jugnauth says he will join opposition party after falling out with country's prime minister.

Mauritius President Anerood Jugnauth has announced his resignation and plan to join the opposition, after falling out Navinchandra Ramgoolam, the Indian Ocean island nation's prime minister.

"I'm not in agreement with the philosophy of the government and the way the country is run," he told journalists on Friday, adding that his resignation would take effect on Saturday. "When I'm not in agreement, I quit," he said.

Jugnauth will be replaced by Monique Ohsan Bellepeau, his vice president.

"He is involved in political strategies to challenge the government, while he should be above politics and upholding the constitution," Patrick Assirvaden, president of the governing Labour Party, told Reuters earlier in the week.

The resignation marks the culmination of a row between Ramgoolam and Jugnauth which erupted when the leader of the opposition in parliament, Paul Berenger, announced earlier this month the creation of a new opposition alliance headed by Jugnauth.

Ramgoolam asked the president, who turned 82 this week and whose role is largely honorary, to either confirm or deny the statement by the opposition, and, in the case of confirmation, to resign.

He is the second head of state to resign since 2002, when then-president Cassam Uteem quit.

Mauritian politics has been dominated since independence in 1968 by a small number of Hindu families, with the last four decades marked by stability and steady economic growth that have propelled the island in to the ranks of middle income countries.