The largest shareholder in Hafren Power has previously been declared bankrupt three times during a lengthy business career.
Another businessman has been declared bankrupt twice but said it should not detract from the project's legitimacy.
Backers claim the £25bn barrage could generate 5% of Britain's electricity.
Hafren Power wants to build an 11 mile (17.7km) barrage between Lavernock Point near Penarth, Vale of Glamorgan, and Brean near Weston-super-Mare, Somerset.
Richard Bazley - the largest shareholder in Hafren Power - was declared bankrupt in 1977, 1994 and 2005.
Mr Bazley, described by Hafren Power as its founder and "the visionary" behind the barrage, describes himself as a "serial entrepreneur".
He declined to be interviewed but Hafren Power chief executive Tony Pryor denied Mr Bazley's background undermined the credibility of the project.
Another founder Idwal Stedman, who sits on Hafren Power's regional committee, has been declared bankrupt twice: in 1994 while working as an architect and in 2006 while working as an antiques dealer.
Although Hafren Power describes Mr Stedman as having run "a highly regarded architecture firm," he is currently barred from calling himself an architect.
He was struck off by the Architects Registration Board last year after complaints about unpaid bills.
The board removed him from the register for "conduct that is fundamentally incompatible with continuing to be an architect".
Mr Stedman has also been the subject of seven separate county court judgements totalling more than £20,000 between 2009 and 2011.
He told BBC Wales in a statement: "Richard Bazley and I originated the idea of a privately funded barrage seven years ago and have worked tirelessly since because we recognised the enormous value of the economic regeneration and clean energy. Without us, there would be no proposal.
"Today the project is maturing and growing, led by a new team of outside business talent. We are still involved and are shareholders.
"Past bankruptcies or mistakes, unconnected to the project, are of course painful for everyone involved. But they should not detract from the legitimacy of the barrage and its importance to Wales and the West of England."
Supporters of the barrage say the privately-financed project could generate up to 5% of Britain's energy needs by using more than 1,000 turbines and tidal power.
But the project cannot go ahead without UK government support. Ministers say they want to see more detailed proposals before they allocate parliamentary time for a bill to allow the project to go ahead.
Neath Labour MP Peter Hain resigned from the shadow cabinet to campaign for the barrage. He declined to comment.
Supporters say the scheme would be financed by sovereign wealth funds and not require taxpayers' cash.
A similar project was rejected by the UK government in 2010 on grounds of cost, but Hafren Power says the revised barrage would overcome that issue and also be more environmentally friendly.
Backers say a barrage would create jobs and help tackle climate change, but opponents warn it would harm the local environment and endanger wildlife.
Serious questions about two of the founders of a project to build a barrage across the Severn estuary have been raised by a BBC investigation.