The Government's selection of Mr Carter for the job has angered Labour, which says it was not consulted over the decision.
Labour's caucus met today and Mr Shearer said afterwards that they will delay a decision on how to vote over the Speakers' role to give National a chance to discuss it with them.
Another MP upset at the choice was National MP Tau Henare - who ended his own bid to be Speaker last year, claiming the Maori Party had reneged on its promise to support him. He said he would "most probably"vote for Mr Carter, but made it clear he still wanted the job himself.
"Damn right I would. 135 years of a continuous democracy and we've had one Maori Speaker, and one female Speaker. That is an appalling indictment on where this country is. Having said that, I'll follow what the boss says."
Earlier in the day, when asked for his view on Mr Carter as Speaker, he said "who?" before walking off and adding "s*** - that will start the year off well".
Mr Shearer questioned Mr Carter's enthusiasm for the job after reports last year that he had preferred to remain as minister.
Mr Carter said today he was looking forward to the job.
"It's a great honour - a great challenge. I don't expect it's going to be an easy time in the House, but I'm really looking forward to it, if I am successful on Thursday."
Mr Shearer also questioned whether Mr Carter was well enough versed in Parliament's rules to be the Speaker.
Mr Carter said he had spent the summer studying Parliament's Standing Orders and Speakers' rulings - the rules by which Parliament is run.
Mr Carter said he was happy to talk to Labour if Mr Shearer wanted him to. Asked why Labour was upset, he said he did not know.
"There's a bit of politics in it, I think."
He said other former Speakers had been elected without unanimous support but had managed to make the transition without too much trouble.
The Greens have confirmed they will not support Mr Carter's nomination for Speaker, saying they do not not agree with his views on funding accessibility for MPs with a disability.
Co-leaders Metiria Turei and Russel Norman spoke to Mr Carter on key issues for the party and high on the list was his view on how he would approach funding to ensure Parliament is accessible to future MPs with a disability and the current funding arrangement for deaf Green MP Mojo Mathers.
Ms Mathers had to fight for Parliamentary Service to fund her electronic note-takers, which enabled her to participate in Parliament fully.
Dr Smith came under pressure to secure long-term funding for the note-taker and it was eventually announced funding had been approved by Parliamentary Service in March last year.
The Greens are concerned there is nothing written into the rules and there was no commitment from Mr Carter to move toward setting a precedent for future MPs with a disability.
Mrs Turei feared a new Speaker may not honour the agreement given there was nothing in writing to protect Ms Mathers' existing entitlement or that of any future MPs with a disability.
"That means parties may be disinclined to have someone with a disability stand as MP,'' she said.
