A senior ally of Jeremy Corbyn dismissed suggestions there was a purge of Labour critics and said a prominent MP’s call on the leader to “call off the dogs” was offensive.
Shadow chancellor John McDonnell claimed Chuka Umunna was “inventing stories” after the senior MP claimed moderates were being systematically targeted by more hardline factions.
Mr McDonnell said the Streatham MP should “just get on with campaigning for a Labour government” instead of complaining about the state of the party.
Mr Umunna, a leading pro-EU campaigner, used a speech on Saturday to call on the leadership to stop using internal divisions as an excuse not to fight Brexit.
His comments came after Tony Blair questioned whether Labour could ever be “taken back” by moderates.
The speech also came in the context of Labour Friends of Israel chairwoman Joan Ryan - a prominent critic of the leadership’s handling of the anti-Semitism row - and Luton South MP Gavin Shuker losing local no confidence votes on Thursday.
Mr Umunna said: “There is now a clear and present danger that this tradition is driven out of our party.
“Having only been re-elected by their constituents last year, already centre-left MPs are being targeted systematically with motions against them for standing up for these values - for demanding we have a zero tolerance of racism in our party.
“More motions such as this are expected by colleagues. My message to our leadership: it is within your power to stop this so call off the dogs and get on with what my constituency, one of the most diverse communities in the nation, demands we do - without equivocation, fight this Tory Brexit.”
However, Mr McDonnell told Sky News: “There are no dogs being called on. I actually think referring to our party members as dogs is just unacceptable.”
It was “an appalling expression to be used about Labour Party members”, he added.
He said “of course there isn’t” a purge but “individual constituencies, if they are dissatisfied with what their local MP has done or said or voted, they will raise their concerns in the traditional way which is a vote of confidence or no confidence, or even just around a particular issue”.
“That’s what’s happening now,” he said. “This is an invented story.”
Mr McDonnell acknowledged it was “outrageous” and “disgraceful” that Iran-backed Press TV was able to film the private meeting in Ms Ryan’s constituency.
“There will be an investigation into that and action will be taken,” he said.
Labour’s conference later this month is expected to debate changes which could make it easier to deselect sitting MPs.
Mr McDonnell said: “There most probably will be a debate about mandatory reselection ... I favour the existing system, which is what we call a trigger ballot.
“I think that works quite effectively but that will be a debate - I can’t see it going through but you never know on these occasions.
“But that’s no threat to anyone, it’s basically saying that within our party our members are the people who decide who represents us and what could be more democratic than that?”