Five leaders of British political parties called for dramatic action to confront climate change in a televised debate on Thursday, just two weeks before the country’s general election.

A melting ice sculpture stole the show.

The sculpture stood in for Prime Minister Boris Johnson, the leader of the Conservatives and the figure who seems to loom over all of British politics. His absence fueled criticism that he has sought to avoid both the public and tough questions from the press during the election campaign.

The ice sculpture infuriated Conservatives, some of whom accused the host network, Channel 4, of partisan bias.

Mr. Johnson did send an emissary in his stead: Michael Gove, a cabinet member who formerly served as the environment minister, but Channel 4 said the debate was for party leaders only.