Department for Education figures show that schools in the city temporarily excluded pupils 25 times for bullying in the 2019-20 academic year.
This was an increase on the previous year, when there were 15 exclusions.
Portsmouth’s figures were in contrast to those recorded by Hampshire County Council, which had seen exclusion rates drop from 68 to 33 in the 2019-20 academic year.
The drop mirrors that across England and comes ahead of Anti-Bullying Week, which begins on Monday.
Despite the nationwide decline during the coronavirus pandemic, children’s charities have warned that bullying in schools is still ‘stubbornly persistent’.
The Anti-Bullying Alliance, which coordinates Anti-Bullying Week every year, said the number of exclusions fell dramatically in 2020 as schools shut during the pandemic.
However, Martha Evans, director of the organisation, said this doesn't mean bullying disappeared from schools, with a survey it carried out this year indicating a rise in cyberbullying.
She added: ‘Sadly, we estimate that at least one child in every classroom is experiencing frequent bullying behaviour from others.
‘We know this experience can affect children’s mental health and have a lingering effect well into adulthood.
‘But we must also remember that the majority of children know that bullying is never okay, and they want positive and respectful relationships with their friends and classmates.’
Of the exclusions in Portsmouth in 2019-20, the majority - 16 - occurred in state-funded secondary schools and nine in special schools.
Childline said the pandemic changed the ‘landscape of bullying’ with much of it now occurring online.
The Department for Education said permanent exclusions should only be used as a last resort, and should not mean an exclusion from education.
A spokeswoman added: ‘Bullying is never acceptable in any form, and we must all take a stand against bullying to create a safe place for all children in the classroom and online.
‘We are supporting schools to tackle all forms of bullying, including through providing funding to anti-bullying charities and ongoing work to improve behaviour.’