'We are making due payment of the sale consideration i.e. $4.2 per mmbtu for supply of gas under the GSPA,' said Reliance Infrastructure vice president Kamal Kant in the letter.

'The charge towards marketing margin is completely illegal (and) contrary to the provisions of the productions sharing contract. We are not liable to make payment of any illegal and unauthorised charge,' Kant added.

'Until this bonafide and genuine dispute with regard to the legality of the charge towards marketing margin is resolved, RIL is not entitled to suspend the operation of the GSPA or disrupt supplies,' he added.

'We are continuing to make payment of the lawful sales consideration at $4.2 per mmbtu and are entitled to receive uninterrupted supply of gas under the GSPA.'