Key changes to the elected presidency proposed by a Constitutional Commission have been broadly accepted, but with some modifications that the Government spelt out in a White Paper yesterday.

The qualifying criteria for private sector candidates will be updated - they must have been the top executive of a company with $500 million in shareholders' equity, to reflect the growth of the economy and the reserves.

But the Government rejected the commission's proposal that candidates, whether from top public or private sector posts, should have served for at least six years, up from three.

Law Minister K. Shanmugam told reporters last night: "We think that might narrow down the field too much, might be too drastic."

He added that someone who has been a top executive for three years would have substantial experience.

The Government also modified the proposal that candidates' qualifying tenure fall entirely within 15 years before the election, saying it is okay if it falls at least partly within 20 years before the polls.

The White Paper - a policy document to explain or discuss matters - said a "cautious approach" was preferred, given other changes to the eligibility criteria.

Prime Minister Lee Hsien Loong said on Facebook that the Government will table a Bill to amend the Constitution in Parliament next month.

There will be a full debate at the sitting after that, in November. Most of the changes should be in place before the next presidential election to be held by next August.

The White Paper sets out the Government's response to the 154-page report of the nine-member commission headed by Chief Justice Sundaresh Menon, which was made public last week.

The panel had been set up by PM Lee to review three aspects of the elected presidency: eligibility criteria, minority representation and the Council of Presidential Advisers (CPA).

Among other things, it recommended that an election be reserved for candidates from a particular race, if no one from that racial group has been president for five terms in a row before that election.

The Government has accepted this recommendation, a key change.

This approach "strikes an appropriate balance" between the long-term goal of multiracialism, and ensuring a president from minority races, the Government said.

The White Paper also addressed concerns that a minority candidate in a reserved election might be a "token" president, saying he or she will have to be eligible and elected.

The Government also outlined other ways it will revise the scheme in the 49-page document.

A six-man council that advises the president will be strengthened.

The CPA will have eight members, and the president will have to consult it on all fiscal matters on the use of past reserves and all key public service appointments.

But a proposal to adjust the threshold needed for Parliament to override a veto based on how much support the president has from the CPA was rejected.

The Government said this approach is more "calibrated" but may unintentionally politicise the council.

It will stick to the present arrangement where Parliament can override a veto with a two-thirds majority if a simple majority of the CPA disagrees with the president.

The commission had also made several suggestions outside its terms of reference, such as urging that the Government decide whether to invoke or repeal a suspended provision of the Constitution to "entrench" or permanently safeguard the powers of the president.

This rule lets the president veto any law that aims to curtail his powers, and a national referendum has to be called to overturn the veto.

The Government will revise the entrenchment framework, but continue to suspend the provision.

The commission also suggested a return to an appointed president, and hiving off the president's custodial powers to a body of experts.

Rejecting this, the Government said the president needs a direct mandate to have the moral authority to veto an elected government's decision.

While there may be tension between the president's custodial role and his historical one as a unifying figure, all elected presidents to date "have been able to perform these two roles with distinction", it said.

"A custodial president democratically elected in a national election remains the most workable and effective solution for Singapore."