SDLP MP Claire Hanna has said planned boundary changes cement her constituency as the "most diverse" in Northern Ireland.
'Belfast South' is to become 'Belfast South and Mid Down' as the constituency is extended to include parts of Lagan Valley and Strangford under final recommendations by the Boundary Commission.
Ms Hanna has kicked off campaigning in new areas coming into her constituency ahead of the next Westminster election expected in 2024.
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The Boundary Commission plans were published last week following a series of public consultations.
Ms Hanna won her South Belfast seat in the 2019 election with a 57% majority, ousting the DUP Brexiteer Emma Little-Pengelly.
But the SDLP believes the boundary changes could make the contest a tougher battle with the DUP next time.
Recent elections in South Belfast have also seen a boost in support for the Alliance Party and Sinn Féin.
The republican party last year made a submission to the Boundary Commission proposing that the South Belfast constituency was axed, dividing it between East and West Belfast.
Ms Hanna at the weekend joined SDLP activists knocking doors in Saintfield, an area which is set to move into the new 'Belfast South and Mid Down' constituency.
Speaking about the changes, she said: "While I'm glad Sinn Féin's proposal to abolish South Belfast wasn't carried, it's frustrating this constituency is always first under the knife.
"I'm sorry to lose some neighbours in Wynchurch and Woodstock, however, it's a big welcome to the neighbourhood for Saintfield and Moneyreagh constituents.
"This further cements South Belfast as the most diverse constituency in Northern Ireland."
She added: "I've been fortunate and delighted to represent the constituency at Westminster since 2019 and will be campaigning hard, on the basis of my record and work rate, to retain the seat in the anticipated 2024 election."
Northern Ireland will continue to have 18 parliamentary constituencies under the Boundary Commission's final recommendations.
The new Belfast South and Mid Down constituency will have an electorate of 71,978 people - an increase on the 70,134 in the existing Belfast South constituency.
Other boundary changes to constituencies include East Antrim, which will take in swathes of neighbouring North Antrim.
Foyle will be reduced in size, with parts of the current constituency moving into West Tyrone and East Londonderry.
The electorate for Foyle will fall from 74,431 to 69,890 under the recommendations.
The Boundary Commission for Northern Ireland is an independent public body responsible for reviewing UK parliamentary constituency boundaries in the region.
Its final recommendations report was submitted to the Speaker of the House of Commons, who has now laid before Parliament the reports from all four UK Boundary Commissions.
The UK Government must submit a draft of an Order in Council giving effect to the recommendations in the reports within four months.
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