Two post offices in Hove will close next month despite community campaigns to save them from the axe.
The Post Office has confirmed branches in Margery Road and North Hangleton will cease operating on Monday, May 12.
The closures follow the shutting of offices in Ditchling Road, Havelock Road and Bates Road in Brighton earlier this month.
It means residents will have to use alternatives in Station Road, Portslade, and at The Grenadier shopping parade in Hangleton.
Residents say many elderly and disabled people in Hangleton will have to get the bus to and from The Grenadier because of steep hills in the area.
Drew McBride, head of area for Post Office Ltd, said: "We fully appreciate the concerns expressed by those who let us have their views and have taken account of them in making this final decision.
"However, the issue is not about the future of an individual branch but the overall viability of our urban network.
"Even with the closure of Margery Road and North Hangleton post office branches, customers will still have reasonable access to alternative branches where they can continue to use post office services they value and trust."
Brighton and Hove City Council liaison councillor Brian Fitch launched a petition against the closures of branches in Margery Road and North Hangleton.
He said people on the Knoll Estate would now have to walk more than half a mile to a post office in Station Road, Portslade.
Councillor Peter Willows, who also campaigned against the closure of the North Hangleton post office, said: "I'm really dismayed. OAPs are going to be given plastic cards and a pin number which they will have to remember and take their pension and money out of a cash machine.
"Hoodlums will just be waiting for them at these machines. This is going to hit the disabled and the elderly the most. I'm very, very disappointed."
Meanwhile, Hove MP Ivor Caplin has demanded Post Office bosses outline the future of postal services in Brighton and Hove.
Mr Caplin and Brighton MPs David Lepper and Des Turner wrote to Post Office chief executive David Mills about the situation last month.
They demanded a halt to further branch closures until a full review of postal services in the city had been carried out but have not received a reply.
The Government has confirmed 3,000 of the UK's 9,005 urban post offices will have to close as Consignia, which owns the Royal Mail and Post Office brands, is losing £1.5 million every day.
Across Sussex, 80 urban post offices, including some in Lewes, are at risk of closure.
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