Labour leader Jeremy Corbyn She also warned that supporters of Mr Corbyn are turning the Labour Party into a “fan club.”It comes after the Telegraph reported that senior Labour rebels are so convinced that Mr Corbyn will win the leadership contest that they are planning to elect their own leader and launch a legal challenge for the party’s name.Speaking on BBC Radio 4’s Today programme this morning, she said believed most MPs opposed a split, “not least because we have been there and done that, and what it did was give Margaret Thatcher unfettered power for a very long time. “Most of us do not want to repeat that experience. If there are those who think it doesn’t matter one way or another. I hope they think very carefully indeed.”It comes after a row between Mr Corbyn and his deputy leader Tom Watson, about whether Labour was being targeted by “Trotsky entryists” Mr Watson last week sent a dossier of evidence to Mr Corbyn to show hard-Left activists linked to former banned organisations were entering Labour, warning of “old hands twisting young arms”. Want the best of The Telegraph direct to your email and WhatsApp? Sign up to our free twice-daily Front Page newsletter and new audio briefings. Labour leadership contender Owen Smith Credit:PA Wire /John Giles She said: “This is not about persecuting some innocent little saint who happens to have become the leader of the Labour Party.”This is about whether or not we have an alternative to the present Government which otherwise will be set free to wreck people’s lives, as I fear that they will.”She said: “In principle everyone should be happy that more people are wanting to join the party, as long as it is the Labour Party they’re wanting to join. “We have had examples of people saying ‘I want to join the Labour Party because of Jeremy but of course if he ceases to be the leader I shall leave’.”Those are not members of the Labour Party, those are members of a fan club.”It’s perfectly nice and legitimate thing to be a member of a fan club and they may get a great deal of satisfaction from it but that doesn’t mean you belong to the Labour Party and I’ll be sorry to think that vast numbers of those people in fact do not really want to be in the Labour Party, they just want to support Jeremy.” Splitting the Labour party would hand the Conservatives the “unfettered power” enjoyed by Margaret Thatcher in the 1980s, Dame Margaret Beckett has warned.The former acting leader said Labour MPs need to think “very carefully” about the impact of a protest split if Jeremy Corbyn wins the leadership election next month. Dame Margaret, who has a seat on the Party’s National Executive Committee, suggested that “vast numbers” do not care about the party and some would be happy to see it split. In an interview with the Observer, Mr Corbyn dismissed the “alleged entryism”, saying that “at no stage in anyone’s most vivid imagination are there 300,000 sectarian extremists at large in the country who have suddenly descended on the Labour Party”. More than 130,000 new members have joined the party in the last six months, many of whom are believed to support the incumbent leader.Dame Margaret urged members to carefully consider how they vote in the upcoming ballot, insisting the contest was not about punishing the embattled “saint”.