Wickremesinghe revealed this during the 'Rata Yana Atha' programme today (28).
The TNL chairman said that he initially inquired whether Gammanpila could join the debate on Monday.
Responding, Gammanpila has said that although he is unable to allot time on Monday and Tuesday, he would be free from 9.00am - 2.00pm on Friday.
Upon inquiring, Warnasinghe too has agreed to the time.
When Gammanpila was informed of this, he has refused, saying that he cannot join a taped debate.
Wickremesinghe said that Gammanpila had evaded the debate in this manner.
Earlier, Warnasinghe had declared that there was no policy reason for Gammanpila to leave the JHU and to form the Pitivithuru Hela Urumaya (PHU).
He had challenged Gammanpila to a TV debate if this was not so and Gammanpila had readily accepted the challenge.