Smith last night announced she was stepping down from her junior ministerial position ahead of an expected reshuffle by Prime Minister David Cameron.
A Cabinet Office spokesman referred questions about her replacement to Number 10, which said it had nothing to announce yet.
Smith’s departure comes as the bill, which is set to introduce a statutory register of third-party lobbyists, enters its third reading in the Commons tomorrow and Wednesday.
The APPC expressed the hope that the bill would be improved by Smith’s replacement for its remaining stages.
"It is a difficult task for any new minister to take on but we very hope they are in listening mode so that we can work with them to make the improvements this bill requires," said APPC deputy chairman Iain Anderson.
PRCA director general Francis Ingham was most critical of Smith's record, saying: "She completely failed to engage an industry that wanted to help her to increase transparency. The facts speak for themselves – Chloe barely spoke to any lobbyists during the Bill’s preparation. The result is a mess of a Bill that will cost a tiny number of consultancies thousands of pounds a year. I strongly urge her replacement to meet with the industry as soon as possible in order to rectify the unnecessarily harmful mistakes that have been made."
The CIPR added it hoped the change of minister would mean "a renewed dialogue" and the chance to "salvage credibility" for the bill.
CIPR director of policy Phil Morgan said: "The concerns raised by the industry and many others, including MPs and Parliament's Political and Constitutional Reform Select Committee, have been hitherto ignored and the result is a bill that has little support and is likely to fail in its first objective of increasing transparency in lobbying."
Smith took over the lobbying bill brief in September 2012 from Mark Harper, who became immigration minister. She has worked with Liberal Democrat deputy leader of the House of Commons Tom Brake, as well as leader of the House of Commons Andrew Lansley, on the passage of the bill.
She said last night that she had written to the Prime Minister on 19 September to inform him she had decided to step down. Her stated reason for the move was to concentrate on being the MP for Norwich North.