Indonesia said Wednesday it hopes to ratify a regional treaty by early next year to fight smog from forest fires that brings misery to millions, but an activist said tougher steps are needed.

"We hope we can ratify the agreement by the end of the year or early next year," the country's Environment Minister Balthasar Kambuaya told reporters.

Earlier Wednesday Kambuaya and environment ministers from four other ASEAN countries, which together form the Southeast Asian bloc's "haze committee", met to discuss ways to prevent the Indonesian forest fires.

The blazes on Sumatra island, caused by the slash and burn method of land clearance for cultivation, left neighbouring Singapore and Malaysia choking in June on the worst haze in more than a decade.

The air pollution scared off tourists, forced schools to close and caused a rise in respiratory illnesses.

Indonesia is the only member of the Association of Southeast Asian Nations which has still not ratified its Agreement on Transboundary Haze Pollution, brokered in 2002.

The treaty aims to stop cross-border smog from forest fires by requiring parties to prevent burning, monitor prevention efforts, exchange information and provide mutual help.

It also binds signatories to "respond promptly" to requests for information from countries hit by the smoke, and to take steps to implement their obligations under the treaty.

T. Jayabalan, a public health consultant and adviser to Friends of the Earth Malaysia, praised Jakarta's move to vow to ratify the treaty but warned that lax law enforcement meant the smog problem would not go away.

"It is a lukewarm measure. You can have all the regulations, but if enforcement is lax, we will continue to have haze," he told AFP.

Jayabalan said large swathes of combustible peatland in Sumatra also meant enforcement would be difficult.

"What we need is meaningful self-regulation. Public health should override profits," he said. "We need a code of practice which includes deterrent measures to prevent burning, where directors of companies are liable to be jailed."

Indonesia has blamed its parliament for the long delay in ratifying the haze agreement.

Jakarta had sought legislators' approval for ratification, but the proposal was rejected in 2008.

The pact has again been submitted to the legislature.

Kambuaya said eight companies are being investigated in connection with the recent haze crisis and the government would identify them "as soon as possible".

He said Jakarta was prepared to share concession maps of fire-prone areas with other governments, but they would not be made available to the public as Singapore had requested.

The concession maps show who has the right to plant crops or log particular tracts of land, allowing them to be investigated and prosecuted for fires.

"We are not allowed to publish concession maps to the public," he said.

Singapore's Environment Minister Vivian Balakrishnan said his country compromised to share such data only among governments "after intense consultations... in the aftermath of the worst haze episode that we have ever experienced".

"We told the other ministers quite frankly that this could not be business as usual," he said in a statement on Facebook. "It is a pity that we could not get greater transparency and public access."

The Sumatra fires have been largely blamed on palm oil firms using the illegal but cheap method of burning vast tracts of rainforest and peatland to clear them for planting.

Besides Indonesia, Malaysia and Singapore, Thailand and Brunei also took part in the regional meeting.

Faizal Parish, senior technical adviser to ASEAN's peatland forests project, said there was no quick fix for the dreaded haze.

"There is no magic wand... it is going to take a long time to reverse the situation," he said, adding that with dry weather expected there could be more haze in the coming months.

burs/jz/sm