Jeremy Corbyn is under pressure to do more to stamp out anti-Semitism in the Labour Party following the suspension of his long-time ally Ken Livingstone.
The Labour leader insisted the party was not in "crisis" after it was announced Mr Livingstone was to face investigation over his incendiary claim that Adolf Hitler had supported Zionism.
However, former shadow home secretary Yvette Cooper said the party had been too slow to respond to complaints of anti-Semitism within its ranks and called for an "action plan" to deal with the problem.
Mr Livingstone's comments came in a radio interview on Thursday in which he sought to defend Labour MP Naz Shah who had been suspended the previous day over a series of anti-Semitic tweets made before she entered Parliament.
Mr Corbyn - who has pulled out of a planned campaign visit to Wales - has insisted the problem was confined to "a very small number of people" in the party.
He said that much of the criticism of Labour's record appeared to come from people who were "nervous" of the strength of the party at local level since he had become leader.
But after a series of senior Jewish figures spoke out over the failure to deal with the problem, Ms Cooper, who unsuccessfully ran against Mr Corbyn for the leadership last year, said more had to be done.
"The Labour Party needs to do more than simply to have suspensions of people who have been saying anti-Semitic things," she told Channel 4 News.
"We've actually got to have an action plan to deal with this in order to have strong processes so that there is swift action because you can never tolerate that kind of discrimination in the party."
Shadow communities secretary Jon Trickett, a close ally of Mr Corbyn, rejected claims he had been slow to act against Mr Livingstone and said the Labour leader would be making a series of announcements "shortly" regarding anti-Semitism.
"Jeremy Corbyn acted within almost moments - certainly within a couple of hours - of hearing Ken's comments, notwithstanding the fact that they have worked together on and off for many, many years," he told BBC2's Newsnight.
However, shadow home secretary Andy Burnham said the party had to act more swiftly when such allegations were made.
"These allegations, when they are surfacing, have not been dealt with properly and quickly enough. They need to be dealt with much more speedily in the future," he told BBC1's Question Time.
Labour MP Wes Streeting, the vice chairman of the all-party parliamentary group against anti-Semitism, warned that inaction by the leadership was damaging the party's reputation.
"What has been most frustrating when it comes to dealing with individual examples of anti-Semitism in the Labour Party has been the flat-footed response of the Labour Party which has given the impression that we are apathetic to tackling anti-Semitism or indifferent," he told BBC News.
"This ostrich strategy cannot be allowed to continue. Our credentials as a party of tackling racism in all its forms is taking a battering."
Labour backbencher John Woodcock said that the party should now release details of the numbers of complaints of anti-Semitism which it has received so that people could see the scale of the problem.
"Clearly these things are recorded and my clear sense is that that number has significantly grown," he said.
He said there was "a particular strand within the hard left" which had been associated over the years with the Soviet Union and who saw the way it had turned "violently anti-Semitic" in the years after the Second World War.
"Some of those people now think that there is an opening within the Labour Party caused by Jeremy Corbyn being elected," he said.