Standards watchdog Sir Christopher Kelly has suggested that the increased transparency on political funding did not appear to have improved MPs' reputation among voters.
The changes were introduced following the sleaze scandals of John Major's 1990s administration.
Sir Christopher, the chairman of the Committee on Standards in Public Life, called on Wednesday for greater openness and better monitoring of anti-sleaze regulations.
He told The Observer: "The (Conway) incident has added to the general feeling that there is something wrong, when the great majority of MPs go about their work with diligence and integrity.
"Perceptions clearly have not improved. Ironically that may be because there is now more transparency than ever.
"What I think Members of Parliament need to consider is whether or not they get greater protection from false accusations that they are behaving improperly if there is actually a greater element of transparency."
Leaders of all three parties have told their MPs to make clear if they employ members of their families.
Labour sources said it was believed between 90 and 95 of their MPs do so, while Mr Cameron has said that 70 Tories employ relatives and the Liberal Democrats said 12 of their MPs do - in total, more than a quarter of the Commons.
