The Pollutant Standards Index (PSI) has inched up to 250 at 11pm on Thursday, up from 231 an hour before.
It soared to a record-high level of 371 at 1pm. The previous record was 226, in 1997.
Air becomes "hazardous" when the PSI breaches 300.
Prime Minister Lee Hsien Loong announced on Thursday there will be a Haze Inter-Ministerial Committee, led by Minister Ng Eng Hen, to tackle the haze problem.
The Ministerial Committee will focus on "protecting public heath and safety, working with the Indonesians to mitigate the haze at source and maintaining economic and social resilience".
It will also review guidelines for protecting vulnerable groups, ensure that society and businesses, especially essential services, continue to operate. Clear guidelines on the protective measures at each PSI threshold will be issued by the committee.
The Prime Minister added he will write to the Indonesian president to register Singapore's serious concerns and repeat the Republic's offers to help.
He also promised to take action against any Singapore companies or companies in Singapore responsible for causing the fires in Sumatra.
Meanwhile, monetary assistance will be provided to Singaporeans who need help with their medical expenses should they fall ill from the haze.
The Prime Minister revealed that the Health Ministry (MOH) will implement a special scheme where those who suffer from respiratory problems or conjunctivitis because of the haze can see their General Practitioners, pay $10, and the MOH will settle the rest of the bill.
This applies to young Singaporeans aged 18 and below, elderly Singaporeans aged 65 and above, CHAS (Community Health Assist Scheme) card holders, PA and Medical Fee Exemption Card holders.
A full list of clinics which fall under the scheme can be found at: www.moh.gov.sg/content/moh_web/home/pressRoom/Current_Issues/2013/haze.html