The libel claim will also allege that the response to the programme from senior Labour figures – including Mr Corbyn, Jon Lansman and Seumas Milne – was a clear breach of the party's commitment to protect the rights of whistleblowers.
Among those believed to be suing the party are former head of disputes Sam Matthews and disputes officer Louise Withers Green.
Mike Creighton, the former director of audit and risk, is another said to be taking legal action.
Their lawyer, Mr Lewis declined to comment when asked by the JC about the launch of legal proceedings against Labour.
But another source told the JC that the five whistleblowers were "determined to clear their names over disgusting smears from the Labour leadership."
The explosive BBC Panorama programme, entitled Is Labour Anti-Semitic?, was screened in July.
On the evening the programme was aired, a Labour spokesman said: “It appears these disaffected former officials include those who have always opposed Jeremy Corbyn’s leadership, worked to actively to undermine it and have both personal and political axes to grind. This throws into doubt their credibility as sources.”
Mr Corbyn later said: "I watched the programme and I felt there were many, many inaccuracies in the programme. The programme adopted a predetermined position on its own website before it was broadcast. We’ve made very clear what our processes are."
Momentum founder Jon Lansman also suggested that the whistleblowers were "former staffers with an axe to grind."
Among the allegations from whistleblowers were claims that key aides, including the director of communications, Seumas Milne, and the general secretary, Jennie Formby, interfered with investigations.
