Reports say a small group of Labour Members of Parliament look set to announce their resignations from the party, senior party sources have said.
Several backbenchers, who disagree with the Labour leadership over its handling of Brexit and the anti-Semitism row, are expected to break away.
But Labour Members of Parliament, Stephen Kinnock, a vocal critic of leader Jeremy Corbyn, has urged them to “stay in and fight”.
Shadow chancellor John McDonnell said on Sunday he did not see “any need for anybody to split from the party”.
McDonnell insisted the party was “holding together on Brexit” and would be “ruthless” on claims of anti-Semitism that have plagued Labour.