The source, who is among the European Commission's chief advisors on sustainability, said that building zero-carbon houses could cost up to £100,000 extra per unit, casting into doubt the possibility of delivering Prime Minister Gordon Brown's target of three million new homes by 2020.
The source said: 'By the time you've added up your shopping list of items to build a zero-carbon house, referred to as Code Level 6 in the Department of Communities and Local Government's (DCLG) Code for Sustainable Homes, you're looking at anything up to £60,000 to £100,000 extra on top of the regular building costs.'
These allegations have been substantiated by several major practices, such as Hunter & Partners, which is currently looking into building its first Code Level 6 zero-carbon homes.
The firm's head of sustainability, Tim Ashton, said: 'We are looking at a small, pilot Code Level 6 scheme at present, and this is currently being priced at around £60,000 per unit over standard comparable housing costs.'
The insider added that even if costs came down enough to make building Code Level 6 houses feasible, the building skills involved are way beyond the current level within the construction industry.
He said: 'We are not even building houses, in bulk at least, to German PassivHaus standards - which is only comparable to Code Level 4 in this country - particularly when it comes to airtightness.
'If we get to German PassivHaus standards by 2016 that would be phenomenal, but to think we can build zero-carbon houses by 2016 is complete science fiction.'
Sheppard Robson's head of sustainability, Alan Shingler, who helped design the UK's first Code Level 6 house - the Lighthouse, at certification group BRE's research site in Watford - agrees that the lack of skills is a major issue.
'There needs to be a complete shift in the construction of houses - a behavioural change. It is meeting the air-tightness parameter that will be the biggest challenge,' said Shingler.
The UK's three largest housebuilders - Persimmon, Barratt and Taylor Wimpey - declined to comment on the 2016 target, but the National House-Building Council (NHBC) was optimistic.
Robert Lockey, service training manager for the NHBC, said: 'Yes, it will be hellishly challenging, and there is a lot of work to do. But I have to say it's possible. First, we need the designers to figure out what works best. When that is decided, we can get on with training people up.'