Labour leadership contender Owen Smith said the party should take on Theresa May and "smash her back on her heels" - but then admitted his choice of language may have "backfired".
Smith said he had been using "robust rhetoric" as part of his pitch to defeat Jeremy Corbyn in the Labour leadership contest.
In a speech aimed at wooing supporters of Corbyn to back his bid to oust the leader, Smith announced plans to appoint a cabinet-level minister to deliver fair employment, end the public sector pay freeze and outlaw zero-hours contracts.
In an attack on May - and Corbyn's response to her at Prime Minister's Questions - Smith said she had the "temerity" to lecture the opposition on social justice and insecurity at work. "It pained me that we didn't have the strength and the power and the vitality to smash her back on her heels," he said.
Smith brushed off suggestions that his comment about May - which was not included in the prepared text of the speech - was at odds with his professed commitment to equality.
He said: "We should be smashing the Tories back on their heels. Their ideals, their values, let's smash them, let's get Labour in.
"It's rhetoric, I don't literally want to smash Theresa May back on her heels, I'm not advocating violence in any shape or form."
But pressed on his choice of language he told 5 News: "Perhaps it backfired, but we should have a bit of robust language in politics, I think."
A spokesman for Corbyn's re-election campaign said: "We need to be careful of the language we use during this contest as many members, including many female Labour MPs, have said they feel intimidated by aggressive language.
"Jeremy has consistently called for a kinder, gentler politics. We should all reflect that in our political rhetoric."