SINGAPORE - A member of the core of the fourth-generation political leadership, Mr Tan Chuan-Jin, 48, will be the new Speaker of Parliament.

Mr Tan will resign as Minister for Social and Family Development to be nominated as Singapore's 10th Speaker by Prime Minister Lee Hsien Loong when the House sits on Monday (Sept 11).

The Speaker's post fell vacant when Madam Halimah Yacob resigned on Aug 7 to contest this month's presidential election.

Taking over from Mr Tan at the helm of the Ministry of Social and Family Development (MSF) is Mr Desmond Lee, 41, who will remain Second Minister for National Development but relinquish his posts as Minister in the Prime Minister's Office and Second Minister for Home Affairs.

The changes were announced by the PMO in a statement on Tuesday (Sept 5).

"PM Lee has briefed PAP MPs on his nomination and received their full support," the statement said, noting that the Speaker cannot be elected from members who are office holders.

"As Speaker, Chuan-Jin will have to preside over Parliamentary debates, and ensure fair and full discussion of national issues," PM Lee added in a Facebook post.

"Chuan-Jin has the temperament and personality for this role."

"It was not easy to find a suitable replacement. While Chuan-Jin stood out as the best choice, it was a very difficult decision to nominate him, as it meant losing an effective and activist Minister at MSF Singapore," he added. "Chuan-Jin remains an important member of my team, though in a different role."

Responding to the announcement, Mr Tan wrote on Facebook: "I'm glad to accept PM's nomination and hope for my Parliamentary colleagues' support."

Mr Tan, a Singapore Armed Forces Overseas Scholar, resigned from the SAF as a brigadier-general in March 2011 to enter politics. He was elected MP for Marine Parade GRC in May 2011 and appointed Minister of State for Manpower and National Development a month later, in June 2011.

He became the Acting Minister for Manpower and Senior Minister of State for National Development in August 2012. In September 2013, he relinquished his appointment at the Ministry of National Development (MND) and a year later, in May 2014, he was promoted to full minister at the Ministry of Manpower (MOM).

In April 2015, he was appointed Minister for Social and Family Development in a Cabinet reshuffle.

PM Lee paid tribute to Mr Tan's contributions at the various ministries. He singled out his deep interest in social issues like helping the needy and disadvantaged families while leading the MSF; and championing the cause of low income workers while he led MOM.

He also noted that while Mr Tan was at the MND," Chuan-Jin built good rapport with the heritage, nature, environmental and animal welfare groups".

"I have asked him to maintain his interest in environmental and social issues, and his concern for the needy and disadvantaged. I am glad he has agreed to continue advising MND on these issues, and to oversee SG Cares, after he becomes Speaker," PM Lee added.

SG Cares is the national movement to build a caring and inclusive society.

Mr Tan will also be appointed adviser to the National Council of Social Service and continue to lead Marine Parade GRC, PM Lee said.

In his Facebook post, Mr Tan thanked PM Lee and his Cabinet colleagues for their trust and support, as well as staff at the MSF and social service sector for their dedication, support and friendship.

He also said that past Speakers had served to the best of their abilities, and in their own unique ways.

"Good ideas can come from both sides of the House, as does good intent. In fact they abound throughout the length and breadth of our society. Our duty must be to harness these for the common good - so as to put them to the service of fellow Singaporeans, and to build a better society. I look forward to doing this as effectively as I can," he added.

The PMO also announced on Tuesday that Mrs Josephine Teo, 49, will be appointed as Second Minister for Home Affairs.

She will relinquish her appointment as Second Minister for Foreign Affairs, and will continue as Minister in the Prime Minister's Office and Second Minister for Manpower.