Blogger Roy Ngerng says his sacking by his employer, Tan Tock Seng Hospital (TTSH), is politically motivated.
In a Facebook post on Tuesday evening, Mr Ngerng said: "I had wanted to give my employers the benefit of the doubt, but the truth of the matter is that the sacking is politically motivated."
TTSH had cited two grounds for dismissal in a statement earlier in the afternoon. It said Mr Ngerng, 33, had misused working time, hospital computers and facilities for "personal pursuits", while his conduct had been "incompatible with the values and standards expected of employees".
Mr Ngerng also said he has been under "immense pressure at work" over the past few weeks, but he has also contributed immensely at work.
He was employed on a yearly contract with TTSH for the past two years as a patient coordinator at the Communicable Disease Centre.
He is currently facing a defamation suit by Prime Minister Lee Hsien Loong for alleging on his blog that Mr Lee criminally misappropriated Central Provident Fund monies.
Separately, the Ministry of Health (MOH) said in a statement on Tuesday that it had been informed by TTSH of its decision to terminate Mr Ngerng's employment contract as well as its reasons for termination.
"MOH supports TTSH's decision as Mr Ngerng's actions show a lack of integrity and are incompatible with the values and standards of behaviour expected of hospital employees," said the ministry.