The Bank of England said the former PM contacted its officials multiple times last year as the finance firm sought access to a Covid loan scheme.
Three MP-led inquiries and a lawyer-led government review are looking at the former Tory leader's work for the company, which collapsed in March.
On Wednesday, the Bank published details of contacts between Mr Cameron and its officials during the early stages of the Covid crisis last spring.
They show the ex-PM contacted Bank officials before and after the firm applied to join a government scheme to support lending to businesses.
These include email exchanges with Sir Jon Cunliffe, the Bank's deputy governor. The Bank was running the scheme, along with the Treasury.
Greensill Capital had wanted the terms of the Covid Corporate Financing Facility (CCFF) to be changed so it could take part in the programme.
The request was ultimately rejected after the Treasury concluded the firm's proposals were not suitable.
Earlier on Wednesday, Sir Tom - the Treasury's permanent secretary, who previously worked for Cameron as a Europe adviser - said Greensill Capital had "persistently" approached his department about being involved.
Giving evidence to MPs on the the Public Accounts Committee, he told them Mr Cameron had rung him directly in April 2020, although the call did not include "substantive discussion" of Greensill's proposals. "It was simply a call to draw it to my attention," he said, adding that Mr Cameron had his work phone number "because I used to work with him".
The second most senior official at the Treasury, Charles Roxburgh, told the committee he had met Mr Cameron and financier Lex Greensill - founder of the firm - at nine meetings spread out over four months from March to June 2020.
The Treasury is shortly expected to reveal further detail about its contact with Mr Cameron and Greensill in response to a Freedom of Information request.