He was "very disappointed that Jamie and other Act MPs won't be joining me in Parliament".
Mr Seymour said he hadn't been approached to take over as the party's leader but didn't rule it out.
"I'd do just about anything to advance Act and its values, but one thing I've said all year is that I want to be part of a disciplined and collegial Act Party.
"We've had far too much trouble in the past from infighting within the party, so whatever we do will be disciplined and collegial."
A meeting with Act's board had been scheduled for "post-election reflection" and to discuss the party's plan, Mr Seymour said. However- he didn't expect the future of the party's leadership to come up.
Act's party vote suffered due to National running a "very, very effective party-vote campaign" which resulted in them pulling off a "historic once-in-a-generation result", being able to govern alone under MMP, Mr Seymour said.
"It's happened once in Germany over 70 years. It's never happened before in New Zealand, but good on them, they pulled it off."
Dr Whyte said his future as the party's leader was dependent on backing from fellow members and Act's board.
"I'm sticking with Act and I'm going to keep working with Act ... It's an unusual arrangement and we need to think through its viability.
"I would like to do it, but we need to make sure it makes some kind of sense so that it can work."
He said he was happy with the party's arrangement with him as the leader and Mr Seymour as its Epsom candidate.
"I think that if I had been the leader and the Epsom candidate we would have basically been saying that Act has no more ambition than to win Epsom - and that isn't true - we want to be a major force in New Zealand politics.
"Act as a brand is a tarnished brand but it is still a powerful brand.
"I don't think we need to rebrand ... if we just keep doing what we believe in, I think we can earn the respect of the population."
Despite rubbishing pre-election polling as being wrong, Dr Whyte conceded that pre-election polls had sealed the party's fate.
The party's polling had increased after he took over as Act's new leader in February but dropped after former Act MP John Banks was found guilty of filing a false electoral return in June, Dr Whyte said.
"There were some reasons to believe that the polls were inaccurate. For example, we thought we were getting quite a lot of support from the Chinese community.
"We came in around where the polls had been so I can't claim to be surprised.
"It's harder for us when National's doing well. It always has been. If you look at our fortunes they're inversely related to National's." APNZ
