Jeremy Corbyn has said he is in the Labour leadership contest “for real”, and has called for renationalisation of the railways and energy companies.
The left-wing MP, who topped a recent YouGov poll, told the BBC’s Andrew Marr Show he was “making no predictions” over the outcome.
The popularity of his campaign has sparked a row within the party,
Ex-SNP leader Alex Salmond said he could work with Labour on “a range of issues” if Mr Corbyn became leader.
Mr Salmond said the Islington North MP was a “substantial politician” and criticised his “demonisation” in the press, saying the two parties could co-operate on welfare reform and Trident renewal.
Former Prime Minister Tony Blair is among those to have warned Labour against moving to the left following a poll that put Mr Corbyn ahead of Andy Burnham, Yvette Cooper and Liz Kendall in the race to succeed Ed Miliband.
It has been suggested that Conservative supporters, as well as “hard left” activists, have been paying the £3 required to take part in the vote in order to back Mr Corbyn.
But Mr Corbyn said he only wanted the votes of “genuine Labour” supporters, who “want to stay for the longer course”.