Green fund to the tune of Rs 1,500 crore is lying largely unused in Delhi as the city battles the problem of pollution.

The lion's share of the amount - Rs 1,003 crore (till November 10) - comes from an Environment Compensation Charge (ECC) imposed by the Supreme Court in 2015 on trucks entering Delhi while the rest is made up of cess on every litre of diesel sold, in effect since 2008.

The Central Pollution Control Board (CPCB) has amassed Rs 62 crore as one per cent cess from dealers selling diesel cars with engine capacity of 2000 cc and above in the Delhi-NCR region following a directive of the Supreme Court in August last year.

The South Delhi Municipal Corporation (SDMC) collects the ECC and hands over the amount to the city's transport department every Friday, Usman Nasim, a researcher with the Centre For Science and Environment (CSE), said.

The cess on diesel was announced by the Sheila Dikshit government in December 2007 as part of its efforts to control air pollution due to vehicular emissions.

The corpus, known as 'Air Ambience Fund', is maintained by the Delhi Pollution Control Committee (DPCC). Over the years, it has assumed a substantial size and stands at around Rs 500 crore currently, Nasim said.

When contacted, a senior transport department official of the Delhi government said that only on Tuesday a decision has been taken to use the fund to subsidise the procurement of electric buses.

"We will use the fund for electric mobility. E-buses are very costly upfront and need to be subsidised in the first phase. Subsequently, running them does not entail much expenditure," the official said.