Chief executive Jack Dorsey admitted during an on-stage interview in Dmexco that the company hadn't thought "cohesively" enough about a solution to harassment on Twitter.
Dorsey was responding to a question from interviewer Martin Sorrell, who pointed to the controversy over Facebook deleting a historical photo of a Vietnamese girl fleeing a napalm attack during the Vietnam war.
Dorsey said: "We want to make sure people have control over their experience, we're not arbitrating a lot of content on the system. That's worked really well for us for the most part.
"We have seen a flare-up in targeted abuse and targeted harassment, which we're being more aggressive about.
"It's something we always knew was important, but we didn't put enough engineering, product and design resources behind it."
He said the company was working on new tools that would make people feel "safe enough" to tweet their opinions. But, he added, the company had always taken a "strong stance" against censorship.
This seemingly contradictory stance has attracted strong criticism from high-profile Twitter users who have faced a barrage of abuse for, apparently, being women, being black, being feminists or being Muslim, among other things.
Dorsey spoke publicly on the issue earlier this year after one star of the all-female Ghostbusters remake, Leslie Jones, quit the service after persistent racist abuse. He tweeted directly at Jones, and the company has said it is investing in more anti-harassment tools. It also banned one Twitter user, blogger Milo Yiannopoulos, over his role in the abuse.
Acquisition and profitability
Dorsey dodged a number of questions from Sorrell over the company's future. Sorrell noted that WPP is a major investor in Twitter on behalf of its clients, funnelling a total of $150m into the company.
Asked whether Twitter might be an acquisition target, Dorsey said there had always been speculation and interest around the company, but that it had a "long-term plan". That comprises focusing on live content such as sports, news and entertainment.
The company will stream its first NFL game tonight, and Dorsey said the company may pursue the same strategy in entertainment. "What gives me confidence is that we're innovating in our core – making our experience better and seeing increases in usage," he said.
Asked why monetising the company had been such a struggle, he replied: "I'm looking more at the long-term of what our service provides. I trust that as long as we're providing the best experience for customers, everything else will take care of itself.
"We will monetise in the right way."