Chime Communications chairman Lord Bell said Bell Pottinger, number one in PRWeek's Top 150, was actively working for the National Transitional Council, although no contract had yet been signed.
'Bits and pieces are going on,' said Bell. 'We are involved in it all, but no one has made any decision and contract. At the moment, the work we are doing for them is informal. Whether we will get in a situation with people in which it will come to something, I'm not sure.'
The National Transitional Council - also known as the Interim National Council or the Libyan National Council - is a political body formed to represent Libya by anti-Gaddafi rebels during the uprising against Colonel Gaddafi's regime.
Its formation was announced in Benghazi in February and it intends to act as the 'political face of the revolution'. The council has so far been officially recognised as the sole legitimate government of Libya by a number of countries including France and Italy.
Bell declined to elaborate on the nature of the work he was doing for the new government.
The news of Bell Pottinger's appointment follows on from the work the agency has been doing for Mohammed El Senussi, the exiled 'crown prince' of Libya, who has been living in London since 1988.
El Senussi is related to King Idris, who was overthrown by Gaddafi in the coup of 1969. Bell said that the work the agency was doing for the crown prince continued.
Bell Pottinger was until recently working for the Economic Development Board of Bahrain and expanded that remit to support the government of Bahrain during uprisings earlier in the year.
The account, thought to be worth well in excess of seven figures annually, was suspended during the three-month period of emergency rule declared in March.