Householders and businesses in Aberdeen will have to use the 01224 code when making local calls from next month.
Communications industry regulator Ofcom is introducing the change from October 1 because of the continual demand for new telephone numbers.
It says the move will enable it to create new landline number ranges that can start with 0 or 1, which means the existing dialling code does not need to change.
Callers will hear a message, which will be free of charge, asking them to redial using the full area code.
An Ofcom spokesman said the number of telecoms companies had increased significantly over the past 10 years, leading to more competition and cheaper landline bills for millions of homes and businesses.
He added that asking people to use the local dialling code would avoid the need for more disruptive measures, such as changing existing phone numbers.
Aberdeen City Council finance convener Willie Young said the changes reflected the fact that the city was “booming”.
He said the growth of businesses, housing and major public sector investment had led to a shortage of telephone numbers.
Mr Young said: “Aberdeen is a city that is growing extensively – it is going like a fair, which is great news.
“This is perhaps a change we could do without but it is part of being a successful city and at least the number is not changing.”
North-east Conservative MSP Alex Johnstone said he was not surprised to hear the news.
“I have heard for some time we are running out of numbers in the Aberdeen area and it is an indication that economic growth is running at breakneck speed, almost uniquely in Scotland.
“For this reason we need to make sure that the proper measures are put in place to expand the number of phone numbers in the future.”
The other areas affected by the change are Bradford, Brighton, Middlesbrough and Milton Keynes.
People making local landline calls in the Bournemouth area have been using the full number since November 1, 2012.