MPs who worked with Mr Michael Palmer reacted with shock and disbelief when they heard the announcement of his resignation and affair.

When contacted, MP Zainal Sapari, who is taking over from Mr Palmer as chairman of Pasir Ris-Punggol Town Council, did not even know the reason why Mr Palmer has quit.

"Wow. I can't believe it," he said, when informed by The Straits Times that Mr Palmer had resigned because of an affair with a People's Association staff member.

He said he was only told of the resignation in the morning by Deputy Prime Minister Teo Chee Hean but was not given the reason. Mr Palmer's former constituency, Punggol East was formerly a part of the GRC.

Mr Zainal, who is currently overseas, said he did not know the PA staff member in question.

Another Pasir Ris-Punggol GRC MP Gan Thiam Poh also expressed surprise at the turn of events. Mr Gan worked closely with Mr Palmer as their divisions were next to each other.

He said Mr Palmer had not been behaving unusually recently, and had always seemed to be "a very nice person, a caring MP and Speaker of the House."

He said: "We want to assure all residents that we will do our best to make sure there is no drop in the service level."

Asked if he thought the incident will affect the public's confidence in the PAP, Mr Gan said no.

"Voters know we are working hard to serve them. This is an isolated incident... Mike made a quick decision, he felt he needed to be accountable for his actions, and he left. So people know that the PAP is a party that emphasises on values," he said.

He added that internally, party members "will continue having faith in the party, knowing we have high standards".

When contacted, deputy speaker of the house Charles Chong said he heard about the resignation just before the media conference, and is still trying to find out more information.

Mr Chong will be Acting Speaker. The Prime Minister will nominate a new Speaker for Parliament's consideration when it next meets.