Leading unions have urged Labour MPs to respect the authority of Jeremy Corbyn as party leader.
In a joint statement, they said Mr Corbyn was the democratically-elected leader of Labour and his position should not be challenged except through the proper democratic procedures provided for in the party's constitution.
The statement said: "The current crisis within the Parliamentary Labour Party is deeply regrettable and unnecessary. Last week's vote to leave the European Union presents the entire labour movement with unprecedented challenges.
"Above all, we need to be fighting to preserve our members' jobs, already under threat in several industries and across the public sector as a consequence.
"The Government is in crisis, but already serious debates are taking place and decisions being made which profoundly affect the interests of working people.
"Under these circumstances, our members and millions of others will be looking with dismay at the events in parliament. It cannot be right to seek to denude the Labour front bench at this time, when the Government more than ever needs to be scrutinised and held to account by an effective and united opposition that does the job it is paid to do.
"Jeremy Corbyn is the democratically-elected Leader of our party who secured such a resounding mandate less than ten months ago under an electoral procedure fully supported by Labour MPs.
"His position cannot and should not be challenged except through the proper democratic procedures provided for in the party's constitution.
"We urge all Labour MPs to abide by those procedures, and to respect the authority of the party's Leader.
"While we have stated that we believe a leadership election would be an unwelcome distraction at this time of crisis, if one nevertheless occurs through the proper procedures we would expect all parts of the party to honour the result and pull together in the interests of the country, and working people in particular.
"The only party that can win for working people is a strong and united Labour Party. "
The statement was signed by the following general secretaries: Len McCluskey, Unite; Dave Prentis, Unison; Tim Roache, GMB; Dave Ward, Communication Workers Union; Brian Rye, Ucatt; Manuel Cortes, Transport Salaried Staffs Association; Mick Whelan, Aslef; Matt Wrack, Fire Brigades Union; Ronnie Draper, BFAWU (bakers union) and Chris Kitchen, National Union of Mineworkers.