Former prime minister Gordon Brown has said Labour can only deliver on its principles in power as he made a high-profile intervention in the leadership contest with a keynote speech.
Mr Brown said he did not aim to attack any of the candidates in a speech that set out to clearly distance himself from support for frontrunner Jeremy Corbyn.
The newly elected Scottish Labour leader has said the long and increasingly petty campaign to replace Ed Miliband is letting David Cameron off the hook.
Kezia Dugdale, who was elected yesterday, said she was concerned that the party leadership contest south of the border would hinder its ability to be an effective opposition in the meantime.
Dugdale also questioned Jeremy Corbyn's willingness to be prime minister, but acknowledged that his popularity and "big ideas" are exciting the country.
Earlier this month, she had questioned how "a guy that's broken the whip 500 times" can enforce party discipline, in an interview with The Guardian.
Former PM avoided naming any Labour leadership candidates in his speech, but appeared to make a veiled warning against electing Corbyn.
A poll rates Jeremy Corbyn as the leadership candidate both most likely to improve Labour's fortunes and damage the party's chances.