SINGAPORE - Former presidential candidate Tan Cheng Bock has filed an affidavit in the High Court to question the timing of changes to the elected presidency.

A Supreme Court spokesman said: "The High Court has accepted the filing of an originating summons and supporting affidavit and documents by Dr Tan Cheng Bock on matters relating to Section 22 of the Presidential Elections (Amendment) Act 2017."

In a Facebook post on Monday night, Dr Tan announced that the High Court had accepted his application filed on May 5.

The Attorney-General's Chambers said in a statement on Tuesday: "We will study the papers when they are served on us."

Dr Tan wants the court to determine whether the Government's counting of the five presidential terms needed to trigger a reserved election is consistent with constitutional amendments to the elected presidency.

The five terms start with the term of former president Wee Kim Wee, who was the first president to hold the power of the elected presidency.

This means the upcoming presidential election this year will be reserved for Malay candidates under a provision to ensure minority representation.

A pre-trial conference for his legal challenge has been fixed for May 22, said Dr Tan.

Dr Tan's move comes on the back of a press conference he called in March this year, during which he spoke out on the Government's decision to implement changes to the presidency this year.

He said then that the upcoming presidential election should be open to candidates from all races, instead of a reserved election for candidates from the Malay community.

The changes, which Parliament approved in November, state that if a particular racial group has not had a president over the past five terms, the next election would be reserved for candidates from that group. This ensures the presidency reflects Singapore's multiracial society.

Dr Tan, 77, said that the late Mr Wee was not elected, even though he performed the role of an elected president after changes to the presidency took effect in 1991. The count, he said, should start from Mr Wee's successor Ong Teng Cheong.

He had also called on the Government to refer its decision to the courts, adding: "I am concerned that the changes were introduced to prevent my candidacy."

In March 2016, after a review of the elected presidency was called, Dr Tan had announced that he intended to stand in the coming presidential election.

"On 1 April 2017, the Government through MCI said I raised no new points that require a response. I responded to say the MCI missed my point. Nothing further was heard on this issue," said Dr Tan in Monday's post.

"Since this is a matter of national importance, I sought to find the legal answer and consulted the best constitutional lawyer I could find," he added.

He turned to top British constitutional lawyer Lord David Pannick, a Queen's Counsel, and gave him documents on the amendments to the elected presidency, including the Commission Report, the White Paper, all relevant Hansard parliamentary reports from Nov 7 2016 to Feb 6 2017, and the Singapore Constitution and related statues.

"I asked him one question: whether the AG correctly advised the Government to specify President Wee's term as the first to be counted on the basis that he was the first President to exercise elected powers," he said.

Lord Pannick said he disagreed with the AG's advice, said Dr Tan, and that Section 22 as it stands is unconstitutional.

"After receiving Lord Pannick's reply, I felt I could not keep his legal opinion to myself. It would be in public interest to have the Court decide which legal view is correct - Lord Pannick or the AG," said Dr Tan.

He added: "I believe this question can be answered without confrontation or hostility. Both the Government and I have the nation's best interest at heart. It is in nobody's interest to have a reserved election that is unconstitutional."

Dr Tan has engaged law firm Tan Rajah and Cheah, and his legal team will be led by Senior Counsel Chelva Rajah. Since the matter is now before the court, "it is only right that I refrain from making any further public comment until the case is decided", he said.

Correction note: An earlier version of this story stated that if a particular racial group has had a president over the past five terms, the next election would be reserved for candidates from that group. The correct statement should be that if a particular racial group has not had a president over the past five terms, the next election would be reserved for candidates from that group. We are sorry for the error.