Neil Lennon hit back at Charlie Nicholas after the former Celtic player said the club had been "cheap" in signing Diego Laxalt on a season-long loan from AC Milan.
The 27-year-old Uruguyan, capped 24 times by his country, joined on deadline day and will compete with Greg Taylor for the left-back spot.
"Listen, if we were to sign Messi and Ronaldo, Charlie still would have found fault with it," Lennon said at a press conference on Tuesday.
"He's been negative, banging the drum about the club for years.
"We switch off to it. I'm not aware of it. I woke up this morning absolutely delighted with a squad of players that we've got and certainly with the Laxalt signing.
"We've come out of the window very strong. People can throw stones at the club, there's no merit, there's no foundation, there's no substance to it.
"We've kept all our best players. We kept Edouard, we kept Ajer, we kept Christie, McGregor, all these players who are big assets to the club. And that's been a difficult thing to do."
Nicholas added that he thought Lennon would be "pretty annoyed" with the transfer business Celtic have done.
"Charlie doesn't speak for me, he doesn't think for me, and to be honest with you, it doesn't resonate one bit here," said Lennon.
"There's too many ex-Celtic players over the years who have constantly been trying to create this negative narrative around the club.
"We are absolutely flying. We're winning all our games and we've won 11 trophies in a row.
"We're not selling anyone. Normally over the years, we sold Dembele, Tierney and other players but in this window we kept them all."