LONDON — Britain’s political crisis intensified on Sunday after its decision to leave the European Union, with the opposition Labour Party splitting into warring camps, Scotland’s leader suggesting that its local Parliament might try to block the departure and many Britons wondering if there was a plausible way for the nation to reconsider its drastic choice.

The hostilities in the Labour Party broke out as the battle lines became clearer among the governing Conservatives, left in turmoil by the vote on the European Union and the subsequent announcement by Prime Minister David Cameron that he would resign once his party chose a successor.

Michael Gove, the justice minister and one of the leaders of the Leave campaign, threw his support to the former London mayor Boris Johnson, the most prominent figure in the anti-Europe movement. Aides to Theresa May, the home secretary, who backed the Remain side in the referendum on Thursday, were calling legislators to seek their support to take on Mr. Johnson.

The British news media reported that close allies of Mr. Cameron were also working to stop Mr. Johnson, reflecting the sense of betrayal on Downing Street over Mr. Johnson’s decision to tie his political ambitions to the movement to leave Europe. Other cabinet ministers were considering whether to run, including Nicky Morgan, the education secretary, and Liam Fox, a former defense secretary.