Former PL president Ramona Attard was sworn in as an MP on Wednesday.
The Labour Party co-opted her to replace Randolph De Battista, who had himself been co-opted and resigned last week. He has been appointed ambassador to international institutions in Geneva.
Attard said she was honoured to be a member of the country's highest institution.
"I am especially honoured to be a Member of Parliament for the government which has the strongest mandate ever," she said.
She said she would work for the "politics that I believe in" including helping people to achieve their dreams, fighting for civil rights and for a stronger economy.
Attard, a lawyer, is a former ONE News journalist and producer. She served as party president between 2020 and late last year.
The new MP is seen as one of the Labour Party's more liberal voices. She recently called for bold action on women's reproductive rights, demanded immediate action.