Labour leadership contender Jeremy Corbyn has issued a plea for unity after his rival Andy Burnham warned that "provocative" comments from the veteran left-winger's supporters risk splitting the party.

Corbyn was the clear leader in nominations from constituency Labour parties (CLPs), unions, MEPs and affiliated organisations at the midnight deadline, with 162 to Yvette Cooper's 121, Burnham's 118 and Liz Kendall's 21 - though Burnham led Cooper in CLP nominations.

However, Burnham was picked as the best leader by members of the public and Labour voters in an opinion poll.

In an interview with the Guardian, he sounded "alarm bells" about comments from Communication Workers Union deputy general secretary Dave Ward, who described Blairites in the party as a "virus" to which Corbyn was the antidote.

"There is a factionalism that is bubbling under here which, to his credit, Jeremy has not (endorsed)," Burnham said. "There is a risk, though, of a split if people talk in that provocative way."

Referring to the period of bitter divisions which led to the formation of the breakaway Social Democratic Party, Burnham added:

"There are dangers here, there are some echoes of the early 80s. Those should ring loud warnings, alarm bells ... Labour needs to reflect on this, and not go down that path."

However, Corbyn called for a "debate embracing all members from all parts of the party" during the postal ballot, which opens on August 14 and leads to the election of a new leader on September 12.

"The leadership election should be conducted with one thought in mind: our objective is to be a united party focused on winning the general election and campaigning across the country, day in day out," said the Islington North MP, who has become the bookies' favourite in recent days after entering the contest as the rank outsider.

Warning against predictions of splits, Corbyn said: "When the dust has settled, we will still all be Labour. Let's conduct our debate on the basis of comradeship and unity in action against the damaging agenda of the Tory Party."

Corbyn had a clear lead in CLP nominations with 152 to Burnham's 111, Cooper's 106 and Kendall's 18. Supporting nominations have no weight in the ballot and members are free to ignore their constituency party's choice, but they offer an insight into the preferences of the most active party members.