The Letterkenny cook ordered staff at his new restaurant venture, The Dining Room at La Stampa Hotel, to remove Knuttel’s paintings.
The chef, 40, said Knuttel’s work was ‘passe’ and wanted them removed.
But Knuttel, whose work is collected by everyone from Robert De Niro to Bono, accused Gallagher of being an idiot.
“Conrad is just an idiot looking for publicity,” he said.
Gallagher rowed back after the row insisting he meant no disrespect to Knuttel.
“Graham is a great artist and I have no personal problem with him whatsoever.
“But they (the paintings) have been hanging around here on the walls for 20 years or so, so it was time for a new look,” he said.
However Knuttel hit back saying Gallagher asked him to draw a painting which featured Gallagher as the centre-piece along with four other great chefs.
“That is the nearest thing he would have ever got to being a great chef,” swiped Knuttel.
The artist said the painting never went ahead as Gallagher never came up with the €5,000 deposit for the work.