eltic have rejected a second bid, in the region of £25m, from Arsenal for Scotland left-back Kieran Tierney.
The English Premier League club, who had previously had an offer of £15m turned down, had been optimistic a deal could be reached for the 22-year-old.
On Friday, Arsenal increased their instalments-based offer for the defender, who is believed to be keen on moving south.
Talks are expected to continue between Celtic and Arsenal this week.
Tierney, who has also been linked with Italian club Napoli, is currently recovering from a double hernia operation and missed Celtic's opening Champions League qualifier against Sarajevo.
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If the deal goes through, he would become the most expensive player in Scottish football history, with a £25m move surpassing the £19.7m Celtic received when striker Moussa Dembele joined Lyon in August 2018.
Tierney, who has been restricted to nine appearances this year, has won four league titles, two Scottish Cups and two League Cups for Celtic.
The news of Celtic's rebuff came as a group of influential Arsenal supporters' organisations, fanzines and blogs joined forces to call for "better leadership" of the club and hit out at Stan Kroenke's "passive ownership".
A total of 16 signatories published a statement on Monday morning demanding change as the Gunners prepare for a third season without Champions League football.
Under a heading of '£WeCareDoYou', the imbalance of the Arsenal board, "soulless" atmosphere at the Emirates Stadium and a lack of transfer strategy are all accusations fired at Kroenke..
