West London-based practice Hamiltons will now complete design work on the project after Camden Council declared itself satisfied that the commercial firm could match Chipperfield for design quality.
Developer Dwyer received planning permission last year for the conversion and extension of the historic Athlone Estate on Hampstead Lane in 2006, which will create 22 luxury flats.
Chipperfield had worked on the designs up to RIBA stage D, drafting in celebrated Swiss landscape architect Gunther Vogt to deal with the historic landscape. He said: 'What annoys me is that I went to nine or 10 meetings with the council and developed a nice relationship. Now I've ended up being the black sheep and fighting them because they didn't stick up for me.'
The committee that originally awarded planning permission to the Chipperfield scheme praised the developer and architect for an 'exemplary' design process. But, fearing he might be replaced, Chipperfield wrote to Camden Council last October seeking clarification, receiving no reply. Then early this year, Chipperfield was informed that Dwyer was considering replacing him.
Dwyer's solicitor, David Cooper, wrote to Camden Council to request that the Section 106 agreement be altered. The council agreed on the basis of assurances from the client about the new architect's brief, and because Hamiltons had three former Chipperfield employees working on the project. But, according to Chipperfield, Camden did not verify this with him.
Hamiltons director David Lawrence denies his firm has done anything wrong: 'We were approached by Dwyer back in the autumn and were asked to carry the scheme through from stage E to L.
'We agreed and waited until everything with Chipperfield had been concluded and the Section 106 agreements were altered. Once we'd been appointed, the 106 clause had been changed.'
A spokesperson for Camden Council said: 'We considered it desirable at the time to have an extra measure of control over the quality of the design by retaining the named architect [then David Chipperfield].
'We received a request from Athlone Estate to change to Hamiltons. The council agreed to the request in May 2007 because replacing the original named architect with the new one was unlikely to result in a failure to achieve the desired quality of design.'
Dwyer declined to comment except to state that it is 'more than happy with the architects it now has in place'.
Chipperfield dropped from Hampstead scheme despite Section 106