LEIGH GRIFFITHS insists he will "silence the doubters" after agreeing a four-year contract to become Celtic's third and final signing of the January transfer window.

Manager Neil Lennon was thwarted in his efforts to also recruit an unnamed Turkish striker on a fairly quiet transfer deadline day in which Joe Ledley departed for Crystal Palace and Mo Bangura was handed a free transfer.

News of Griffiths' imminent signing from Wolverhampton Wanderers sparked a mixed reaction among the Celtic support, with some fans believing he is not an upgrade on the strikers already at the club. Others were critical of signing a player with a history of off-field problems. The former Hibernian striker, however, vowed to "keep his nose clean" with regards to his behaviour, and confidently predicted he would prove wrong those who doubt his ability.

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"To come to the biggest club in Scotland is the biggest honour you can get," said Griffiths who wasn't registered in time to face St Mirren tomorrow. "I was lucky enough to play for my boyhood heroes Hibs, but you can't turn down the chance to play for a club like Celtic in the Champions League. I'm confident I can silence the doubters. You saw what I did last season for Hibs [he scored 28 goals]. In a team like Celtic, you are always going to get chances. Hopefully they fall at my feet and I can put them away."

Griffiths also hoped to repay Lennon for his persistence after Celtic's first two bids for the player were turned down.

"I spoke with the manager earlier and it was a good chat," he added. "He told me what is expected of me as a Celtic player, saying you can't do anything wrong or people will pick up on it. It's about keeping my head down and working hard to try to prove wrong the people who say I'm not good enough. I also want to prove the manager is right for signing me.

"He's been very positive about me in the press already this week and I just want to get out there, score goals and repay him. I want to show everybody why he brought me to the club."

Griffiths also dispelled any suggestion that he was a character forever drawn to trouble. "Everybody has a past. I just want people to concentrate on what I do playing for Celtic and forget about everything else. I want to be judged on what I do on the pitch and in training. Yes, I have been daft in the past but when I come to training I do my work."

Celtic had hoped to add another striker yesterday but were thwarted in their attempts to sign an unnamed forward from Turkey despite meeting the player's £2.5m release clause. "That was frustrating because we feel he's a good player and maybe we'll revisit it in the summer," said Lennon. "It was just issues on their side with the Turkish club not really wanting him to go.

"It was starting to get a bit messy and the wages began to go up and up. So it didn't get done. But we did everything the right way."

Celtic also lost midfielder Ledley who signed for Palace shortly before the 11pm deadline after the clubs agreed a fee earlier in the day. The Welshman, who had been with Celtic since 2010, would have been out of contract in the summer and the club decided to cash in on him now rather than lose him for nothing at the end of the season.

Celtic also bid farewell to Bangura. The Sierre Leone international had cost £2.2m when he signed from AIK in the summer of 2011 but failed to score a single goal during his time in Scotland. After sending him on two loan spells back in Sweden, Celtic elected to cut ties completely with the player by releasing him from his contract.