Councillor Jeanette Smith will now serve Baffins as a non-aligned independent representative and has resigned her position as cabinet member for resources.
Cllr Smith, who had been a Lib Dem member for two years after leaving the Labour Party, said it was 'sad' but 'the right decision.'
She said: 'I didn't feel that the decisions the Lib Dems were making were for the benefit of the community and more for the benefit of themselves.
'It is not the other Baffins councillors at all. Both Cllr Darren Sanders and Cllr Lynne Stagg are good councillors and are very community minded.'
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For Cllr Smith inequality within the council was a concern, as well as the recent controversial decision to implement the MD residents' parking zone in Southsea.
She added: 'Inequality for me was an issue. At an interview next week for the director one post, which is a role that deals with resources, the panel was all going to be male. How is that representative?
'And I felt that in terms of the MD zone they didn't listen to residents. I know residents wanted a parking zone but the times were not correct.
'I will still work for my residents and the community. This was the right decision.'
Council leader and Lib Dem boss Cllr Gerald Vernon-Jackson praised the work of Cllr Smith. 'I am grateful for all her work and I am sorry she won't continue with us.
'In terms of the interview panel I made it clear that it was not acceptable to have all men and invited Jeanette to sit on it. I completely agree it should not all be men and we wanted to change that.
'And there was a long decision making process for the MD parking zone at a meeting last week. Parking zones are difficult and this one was particularly difficult because it affected residents and businesses.'
The Lib Dems are still the largest party in Portsmouth City Council, with 17 councillors. The Conservative Party has 16, Labour has six and there are now three independent councillors.