The shadow health minister said the new leader will have won the right to pursue their agenda but made clear that she is likely to become a frequent rebel if the Islington North MP takes the top job.
In her final speech of the three-month contest just 50 minutes before voting closed, Ms Kendall appeared close to tears as she warned that Ed Miliband’s successor faces huge challenges to bring the party together after the “tumultuous and divisive” contest.
The Blairite candidate, who has been dubbed “Tory-lite” by some critics, conceded she may have been too harsh in the way she had set out her pitch.
“Perhaps I was too blunt, especially at the beginning when so many party members were still reeling form our terrible defeat. But my view is that in politics, as in life, you cannot deal with problems by ignoring or avoiding them,” she said in a speech in central London.
Ms Kendall said modernisers in the party must recognise some members “doubt our principles altogether”.
But she said Mr Corbyn would consign them to opposition and again said she would not serve in his frontbench team.
“The programme Jeremy Corbyn offers is not new. His policies and politics are the same now as they were in the 1980s and will end up delivering the same result.
“Neither is he the sole keeper of Labour’s principles. No-one has a monopoly on being led by their conscience,” she said.
Ms Kendall said she would not compromise her principles on issue including Britain’s membership of Nato, the renewal of Trident or membership of the EU.
“I’m a person of principle. I think it would be a disaster for the country,” she added.
“I want to be loyal to the Labour party whenever I can but there are some things I believe are so important for the future of the country that I will do what my conscience tells me.”