Labour leadership candidate Lisa Nandy said there has been a "vacuum of leadership" at the top of the party.
Speaking to BBC Radio 4's The World This Weekend, the Wigan MP said: "Throughout our entire Labour history, we have never achieved real change in this country by taking the path of least resistance.
"We have to go out, win the argument and to do that most of all we have to make the argument.
"For the last few years what we've had is a vacuum of leadership across the party over issues like Brexit.
"And because of that what you've tended to find is that in both Leave and Remain areas the only way that our activists and our councillors could persuade the public that they were on their side was to stand against the national Labour Party."
Ms Nandy is one of four leadership hopefuls, including Sir Keir Starmer, Rebecca Long-Bailey and Jess Philips, who have already secured the 22 nominations required to progress to the next stage of the contest.
But other rivals Emily Thornberry and Clive Lewis have until 2.30pm on Monday, January 13 to secure enough votes. But as of Sunday, Ms Thornberry, the shadow foreign secretary, had only 10 while Mr Lewis had just four.
With a significant numbers of MPs yet to decide who to back, Ms Thornberry said at the weekend she was "fairly confident" of making it but Mr Lewis admitted getting the numbers was "hard".
In the race for deputy leader, which is running in parallel, two candidates - shadow education secretary Angela Rayner and Ian Murray - are already through.
Three others - Richard Burgon on 18, Rosena Allin-Khan with 17 and Dawn Butler with 15 - are hoping they can also make the cut.
Those who qualify in the two contests then need to get the nominations of 33 local constituency parties or three Labour affiliates - including at least two trade unions - to enter the final postal ballot of party members and registered supporters.
Over the weekend, the left-wing activist group Momentum, which helped propel Mr Corbyn to the leadership in 2015, said it was recommending support for Ms Long-Bailey and Ms Rayner.
It will now ask its members whether they agree with the recommendations, with ballots - consisting of just two questions - to be sent out this next week.
The group's backing for Ms Long-Bailey is unsurprising given that she has long been the favoured candidate of the left to take on Mr Corbyn's mantle.
However, many Corbyn-supporting MPs are backing Mr Burgon, the shadow justice secretary, for deputy rather than Ms Rayner, and Momentum's support will be a significant boost for her campaign.
Although she already has the support of her close friend Ms Long-Bailey, Ms Rayner is distrusted by some on the left after backing Andy Burnham for leader in 2015 rather than Mr Corbyn.
Reports have suggested some around the Labour leader believe she was responsible for trying to undermine him.