The incoming president of Indonesia is backing Singapore's plan to levy bigger fines on overseas polluters. A year after the city-state endured its worst-ever air quality, Singapore presented a bill to parliament this month that would subject foreign companies to fines of S$2 million (HK$12.5 million) for illegal emissions, up from S$300,000. Indonesia and Singapore have long argued over the smoke that blows in from land-clearing fires in Sumatra. Joko Widodo, who won this month's presidential election, agrees that companies implicated in unlawful fires may be fair game for Singapore's enforcers. The sticking point is the sovereignty of Indonesia, where officials have yet to ratify the Association of Southeast Asian Nations' 2002 treaty on haze, which requires nations to act against forest fires and cooperate with neighbours. "We should have some detailed protocols to guarantee the sovereignty of Indonesia," said Sonny Keraf, Indonesia's environment minister from 1999-2001 and Widodo adviser. "But we do appreciate the commitment of the government in Singapore to penalise these companies' activities." Accelerating deforestation makes Indonesia the world's third-largest emitter after China and the United States, according to the World Bank. An outbreak of fires in Riau, a centre of Indonesia's palm oil and paper industries on Sumatra, was blamed for last year's record smog in Singapore. Singapore's Pollutant Standards Index peaked at 401 in June 2013, 100 points above the "hazardous" threshold. While the index hasn't topped 100 in 2014, an El Nino weather pattern may bring worse smog this year to the region, said Environment Minister Vivian Balakrishnan. The fines require Indonesia to help with gathering evidence in its territories, which may be seen as infringement, said Eugene Tan, an associate professor of law at Singapore Management University. The city would need "watertight" evidence to win in local courts, he said. The Indonesian parliament hopes to approve the bill in September before current legislators end their terms.