Lambeth councillors have approved plans to remove on-site affordable housing from a riverside development on Albert Embankment.
Plans for the Rogers Stirk Harbour-designed 28-storey tower on the site of former government offices at Eastbury House were first approved in summer 2012.
The scheme included 14 shared ownership homes spread over two floors but developer St James has now won permission to replace these flats with six private sale flats in the same space.
Instead St James will build 6 social rented homes as part of a nearby scheme which will also provide new offices and classroom space for Vauxhall City Farm.
The variation won unanimous backing from Lambeth's planning applications committee on Tuesday night.
"Officers consider that the proposal is a much better offer for the council, better meeting local priority housing need," said Lambeth planners in their report to members.
The homes on the farm site will be managed by Lambeth Living, the council's arms-length management organisation.
Cllr Pete Robbins, cabinet member for housing, said: "Family sized homes are badly needed in Lambeth and although these are off site, they are just round the corner, are of better quality and will be for social rent.
"This is an example of imagination, collaboration and pragmatism which means looking beyond the headline figure on affordable housing to the quality and type of homes that will be provided for local people."
The Albert Embankment building is now being marketed under the Merano Residences name. A 2-bedroom flat on the 10th floor is currently being advertised for sale for £2.15 million.
The developers held a launch event for the scheme in Abu Dhabi earlier this year.
Merano Residences is due for completion in 2017.