The Liberal Democrat candidate won yesterday’s by-election with 444 votes, 55.8 per cent of the ballot.
The by-election was called following the resignation of Conservative Gillian Keegan earlier this year due to her parliamentary commitments as an MP.
Cllr Kelly said: “This is a fantastic result not only for the Liberal Democrats but also for the people of Rogate and the surrounding villages.
“They felt abandoned when their previous councillor was elected as an MP and stopped attending parish and district council meetings.
“It is a strong message to the Conservatives that they cannot be complacent and treat their constituents with such disregard.”
Mrs Keegan responded with her congratulations to cllr Kelly and said residents were welcome to continue contacting her with their issues for her help as an MP.
It is the first time in 11 years that the Liberal Democrats have contested the seat, which has been held by the Conservatives for the last three elections.
Cllr Kelly, who is also a county councillor for Midhurst, will serve on Chichester District Council until May 2019.
Results were as follows, with the previous election’s percentage in brackets:
Liberal Democrat: 55.8% (+55.8)
Conservative (Robert Pettigrew): 40.1% (-27.3)
Labour (Ray Davey): 2.6% (+2.6)
Green (Philip Maber) : 1.5% (-18.2)
No candidate stood for UKIP (-12.9).
Turnout for the election was 40.45 per cent.
Mrs Keegan said: “I would like to congratulate Councillor O’Kelly on becoming the District Councillor for the Rogate ward.
“I very much enjoyed the three and a half years I served as the District Councillor for Rogate, Rake, Milland and Linch and I would like to thank the residents for their support and for giving me the opportunity to learn more about local government and the vital public service it provides.
“When elected to Chichester District Council I, of course, planned to serve the full term until May 2019 however the snap general election and resignation of my predecessor took everybody by surprise, not least me!
“Whilst I have been unable to attend all of the district and parish council meetings since being elected due to commitments in Parliament I have continued to raise residents’ issues at meetings that I regularly have with the Leaders of Chichester District Council and with the South Downs National Park Authority.
“As their Member of Parliament, the residents of Rogate, Milland, Rake and Linch are often in touch with me by email, phone and some frequently text my mobile or call my home number so I am always available to deal with their concerns.
“Conservative led Chichester District Council is, in my view, one of the best run councils in the country and they do a great job providing excellent services whilst keeping costs under control.
“I learned a lot as a member of the council and cabinet and I’m delighted that in my role as Member of Parliament I can continue to work very closely with my Councillor colleagues and serve residents across the Chichester constituency.
Mrs Keegan confirmed she was resigning in February this year. Speaking at the time, Mrs Keegan said she had been waiting for the Conservatives to find an alternative candidate for her seat.