Stephen Bingham, 53, and Graham Smith, 33, are being investigated for fraud by the Government's Department for Business Enterprise and Regulatory Reform after closing Bramley-based Macroloft Conversions Ltd in July 2007.
Scores of customers were left with work unfinished and heavily out of pocket having paid in advance for work which was never done.
Others said they were duped by the firm after learning projects lacked planning permission. They were left to pay substantial sums to have them removed.
Now the business partners have wound up 1st Call Conversions Ltd, which they established in July. It traded from Beeston Royd Industrial Estate on Gelderd Road in Leeds.
As yet it is unclear exactly how much the new firm has cost members of the public. Macroloft owed 78 individuals, several companies and the public purse £250,000.
A dozen complaints, about unfinished extensions, poor workmanship and rejected planning applications, have been lodged against 1st Call Conversions with WYTS in the past month.
David Lodge of trading standards said that the information has been passed to the Department for Business, who have pledged to take another look at the situation.
Mr Lodge said: "We will be looking into its (1st Call Conversions Ltd] trading activities as a company in light of what has happened previously."
John Battle, MP for Leeds West, helped householders in the aftermath of Macroloft, winning residents the right to keep illegal loft conversions after they argued misrepresentation. He has fiercely criticised an "archaic system" which allows directors to continue to trade while they are under investigation.
Mr Battle has again urged the Department for Business to take action. He said: "It is not right that these businessmen are swanning around in their flash cars while so many people suffer. It is immoral."
Ron Wilson, director of the Federation of Master Builders (FMB) for Yorkshire, refused to renew the directors' membership after Macroloft closed. He said about the latest closure: "It's despicable the way that they have traded. It's a scam and it wants to be taken to the Government."
Robert Lafferty who lives in Kippax has been waiting for three months to get building regulations clearance on a £20,000 extension at his home.
He said: "We suspected that something was seriously wrong. I guess my five-year guarantee doesn't count now. It's just so frustrating. We have spent so much money on a room we can't use."
Work is also unfinished on a number of properties in Ilkley, Bradford and Leeds postal areas LS6, LS16, LS29 and LS14.
Julie and John Brotherton, of Brotherton Skip Hire in Otley, say they are owed £2,500 by the firm.
"When you are a small business it really does affect you," said Mr Brotherton.
Stephen Bingham joined forces with property manager Graham Smith in October 2004, who bought a 50 per cent sharein Macroloft at a cost of £50,000.
The firm grew rapidly, with turnover doubling to £952,000 within two years. A year and a half later the firm was placed into voluntary liquidation. Former customers say the firm should have stopped trading sooner.
The YEP has attempted to contact the principals of 1st Call Conversions by visits, telephone and email, but has had no response.