Malaysia has urged its neighbour Indonesia to sign up to regional plans for fighting pollution from forest-clearance fires.
A thick haze has been spreading across several countries, with visibility in some places down to 200 metres.
Indonesia is the only country in the 10-member Asian regional grouping not to formally approve plans to co-ordinate a response to open burning.
The situation has forced Singapore to issue a health warning.
Large parts of Indonesia, Malaysia and Singapore have been hit by smog from illegal bush fires burning on the islands of Sumatra and Borneo.
Pungent smoke from the fires is an annual problem across south-east Asia during the dry season.
Flights have been cancelled, cars have put their headlights on in the middle of the day and Singapore has warned citizens against taking exercise outdoors.
The worst case of smog ever recorded was in 1997, when a choking cloud engulfed large areas of south-east Asia, costing local economies billions of dollars.
Our correspondent in Kuala Lumpur, Jonathan Kent, says the the smoke form this year's fires is less severe than last year but the fact that the annual smog has reappeared at all has caused annoyance.
Waiting for Indonesia
Saying Indonesia was "dragging its feet", Malaysia also asked for offending firms to be prosecuted.
Malaysian Environment Minister Azmi Khalid said he did not know why Indonesia was "dragging its feet" over the agreement on Transboundary Haze Pollution (THP) approved in 2002 by the Association of Southeast Asian Nations (Asean).
The THP agreement envisages the creation of a regional co-ordinating centre for reacting rapidly to the haze, which is mostly attributed to slash-and-burn farming methods.
Mr Amzi told the BBC that his counterparts in Indonesia assured him in June that they had plans in place to prevent a repeat of the haze. However, he says these do not seem to be working.
Indonesia has outlawed using fire for land clearance but the laws are widely flouted in remote areas of the country and the government seems helpless to control the situation, says the BBC's Lucy Williamson in Jakarta.
Environmentalists say the problem has become more serious in recent years due to timber and oil palm companies clearing land for plantations.
"The fires are seasonal and very predictable, but the government never implements effective measures to prevent and manage them," a spokesman for Indonesian environmental group Save Our Borneo, told AFP news agency.