Miloon Kothari, UN special rapporteur, said a vast swath of the money raised following the disaster has yet to be spent rebuilding the affected areas around the Indian Ocean.
The architect said the timescales put on the reconstruction effort were too slow and unproductive.
'When we see figures saying funds have been disbursed but have not been utilised that is very disturbing,' Kothari said.
'It should really not take this long to build permanent housing. I do not accept the explanation that it is going to take four to five years, in some cases, seven.
'I'm an architect, I know how long it takes to build a house,' Kothari added.