Norwich City transfer target Gary Hooper has reportedly rejected the offer of a Celtic contract extension amid speculation the Canaries have made an improved bid.

Talksport claim the Canaries have failed with a second firm enquiry for the in-demand striker after an initial £5m offer was dismissed by the Bhoys last week - prompting Parkhead chief Neil Lennon to publicly state it fell well short of Celtic's valuation for a striker who has 18 months left to run on his current deal.

The national radio station insisted on Tuesday morning that has not deterred the Canaries, with City captain Grant Holt reportedly an option in an improved player-plus-cash bid to try and tempt Hooper south.

Lennon's assistant, Johan Mjallby, admitted yesterday Celtic were lining up potential replacements if the 24-year-old departs in this transfer window. Burnley's prolific forward Charlie Austin has been touted as likely alternative and the candid Mjallby confirmed he is on the Bhoys' radar.

'He might be on the shortlist,' said Mjallby. 'Charlie is a proven goalscorer and he might come in handy in the future. But right now we think Gary will stay on, at least until the summer, and that will be great for the club. He is a top-class player. It's not only his goals, the last couple of months have shown he is improving his all-round game. We can use him in midfield as well because he is a very clever player.

'We want to keep him because he is improving and making the team better. Gary has proven to be the best goalscorer for us so that's one of the reasons we want to keep him. We always have a shortlist for players in each and every position but right now we are just thinking about Gary staying because he is a very important figure for our squad.'

The Daily Record claimed earlier this week City will need to significantly increase their original offer to entice Celtic to do business in January. This time last year, Celtic reportedly turned down a £7m offer from Southampton for the man who cost them £2.4m when he signed from Scunthorpe in 2010.

'We don't want Gary Hooper to leave. I think he is very happy here. He put in a great performance the other day,' said Mjallby, after Hooper ignored the mounting speculation on his future with a brace in a 4-1 win over Hearts. 'He is enjoying his football, he is enjoying playing for Celtic and enjoying his team-mates. Not only his goals at the weekend, but his general performance was very, very good. The only bid has been from Norwich but we expect there are going to be offers for our best players anyway. That's the way it is in this climate. Even if you get a lot of money for Gary, if a bid comes in and the board and everyone thinks it's good enough, it's always a gamble because money doesn't always buy you a good player. Right now we know what we have got, we have a good squad and players we know and how they function. If you buy a new striker, you never know if it's going to be successful or not.'

Hooper is likely to be in action again tonight when Celtic attempt to move further clear at the top of the table against Dundee United. Hoops' team mate Adam Matthews believes the lure of a forthcoming Champions League last 16 tie against Juventus is a big reason for Hooper to stay put.

'We don't want to sell him, he's enjoying it here and I think he wants to stay,' said Matthews. 'Everyone is looking forward to Juventus, it's a massive game. Gary himself is looking forward to it, so as far as I know he's happy to stay and I'm hoping that is the case. In the current market, Gary is worth way more than that (£5m). He showed against Hearts with the goals he scored that all of the talk isn't going to affect him and he just has to keep it going.

'He's quality as a player and quality as a goalscorer, so when you get someone like him in the box, you are going to get goals.'