MPs also heard there was not "clear information" within the FCA as to how its contact centre should process and refer information about potentially dangerous companies.
Dame Elizabeth said: "It is very important that contact centre call handlers should not reassure consumers about the activities that are not regulated of authorised firms.
"There must be clearer instructions for call handlers that they don't give off-the-cuff advice or so-called advice."
Dame Elizabeth said if there had been a "joined up system" between the call centre and the FCA's handling of financial promotion breaches under its watch "things would have been very different".
She warned it was "pretty appalling" that consumer concerns heard by the regulator's own contact centre regarding the company had not been "escalated appropriately".
The Treasury Committee was told how the scandal-embroiled London Capital & Finance was repeatedly allowed to breach financial promotion rules under the FCA's watch despite repeated reports from consumers.
Dame Elizabeth added: "Although the FCA had a repeated financial promotions policy, it wasn't sufficiently robust.
"One of the real wickednesses is LCF was frequently breaching the financial promotions rules and nothing was done about it.
"If that information had been put together with other information, something might have been done much earlier."
HM Treasury first requested the independent LCF investigation in May 2019 after the mini-bond provider collapsed owing more than £230m and putting the funds of some 14,000 bondholders at risk.
Dame Elizabeth's investigation concluded bondholders were "entitled to expect, and receive, more protection from the regulatory regime in relation to an FCA authorised firm than that which, in fact, was delivered by the FCA".
It also warned the permissions granted to the company were not appropriate for the business it carried out and the FCA had not "adequately supervised" London Capital & Finance's compliance with the regulator's own rules.
The FCA has since apologised for its actions, with chairman Charles Randell admitting there were a "number of things" it could have done better in its supervision of the company.