WASHINGTON — Aides to President-elect Donald J. Trump announced Wednesday night that his transition team would not include lobbyists and that members of the administration would be barred from lobbying for five years after they left government service.

The announcement, made in the first transition conference call with reporters, was an attempt to make good on Mr. Trump’s promise to “drain the swamp” in Washington. It was also a reaction to criticism that some of the original transition team members were lobbyists from interests they were being assigned to oversee.

Under the rules, announced by Sean Spicer, a transition spokesman, lobbyists joining the Trump team would have to terminate their formal registration to lobby. Aides to Mr. Trump said several of the firings in recent days were part of an effort to enforce the new rules, though they declined to reveal any names.

Others have described the firings as part of an effort by Jared Kushner, Mr. Trump’s son-in-law, to rid the transition of connections to Gov. Chris Christie of New Jersey, who was ousted last week as the head of the transition. Aides have denied those reports.