APCO had begun talks with WorldCom about PR strategy prior to the crisis, but the accounting revelation last month dramatically changed the brief.
APCO chief exec Margery Kraus said: 'The commitment initially was to being forthright and honest. That commitment has increased because it is an important way to operate.'
Since the scandal was made public, the company's message has focused on demonstrating its full co-operation with the authorities.
Just over a week before the news broke, CEO John Sidgmore told shareholders the company was embracing a new commitment to comms.
WorldCom had been plagued by debts and a share price that plunged from around £40 in April 1999 to 92p this week.
Kraus said the firm's task now is to be forthcoming with investigators, while emphasising that its current woes were the responsibility of the previous management team, led by former CEO Bernard Ebbers.
'It's a new person running the company, and his way of running it is to let people know what he knows, when he knows it,' she said.
On 2 July, the day after the accounting revelation, Sidgmore answered questions at a press conference held at the US National Press Club.
WorldCom has also released a letter from Sidgmore to President Bush.
'Seven weeks ago, as I assumed the position of CEO of WorldCom, Bert Roberts, our chairman, and I pledged to restore trust in this company,' read the letter.
'Restoring trust means being straight about problems as we discover them - and aggressively solving them,' it added.