LONDON — Mark Zuckerberg, Facebook’s chief executive, has struck a conciliatory tone in the wake of a data-privacy scandal. That was not the case on Wednesday for the former chief executive of Cambridge Analytica, a consulting firm at the center of the controversy.

Alexander Nix, who led Cambridge Analytica until it suspended him in March, defiantly shot back at accusations from British lawmakers that he or his company engaged in unethical business practices, abused information pulled from the social network or played a role in the British vote to leave the European Union.

In a contentious hearing before Parliament’s media committee, Mr. Nix said Cambridge Analytica did at one point have data on millions of Facebook users. The data was harvested from the social network without the users’ consent. But, he said, Cambridge Analytica didn’t find the information useful and deleted it after a request from Facebook.

His comments contradicted evidence presented by a former Cambridge Analytica employee, Christopher Wylie, who has said the data was central to Cambridge Analytica’s political consulting work for Donald J. Trump’s 2016 presidential campaign. Mr. Wylie has also suggested that Cambridge Analytica did advising work for the Brexit vote.