LISBON - Portuguese Foreign Minister Paulo Portas on Tuesday said he would quit the government, a day after the shock resignation of the country's Finance Minister Vitor Gaspar.

Portas, who is also the leader of the junior partner party in the coalition government, said in a statement that that he opposed the appointment by Prime Minister Pedro Passos Coelho of Secretary of State of Treasury Maria Luis Albuquerque to replace Gaspar as the new finance minister.

He said his decision was "irrevocable."

"I expressed my opinion to the prime minister in good time. Consequently, and taking into consideration the decisive importance of the finance ministry, staying in the government would be incorrect. Neither politically nor personally sustainable," Portas said.

This is the third minister in the coalition government to leave office after Miguel Relvas stepped down as minister of parliamentary affairs in April in the wake of a scandal surrounding his university degree.

Monday's shock resignation of Vitor Gaspar, the architect of the country's reforms under its EU-IMF bailout, even triggered calls for an early election.

So far, Portugal's PSD or Socialist Democratic Party has been supported by CDS/PP or People's Party headed by Portas in a coalition government since the parliamentary elections in June 2011.

Portas has been in odds with the coalition government over its tough austerity measures, the reduction of pension in particular, under a 78-billion-euro ($101.23) bailout agreement with international lenders.