May I just add something? If I understand your question properly, you're referring to a lobbying firm or a firm that's in the government relations business, as opposed to a firm that's in the manufacturing industry, in which case these are considered consultant lobbyists. The 20% rule, the significant part of duties, does not apply to consultant lobbyists. It only applies to firms that have in-house lobbyists for their firm, like a manufacturing company that has a government relations unit within it, as opposed to hiring a consultant from outside.
On December 13th, 2011. See this statement in context.