The Shadow Foreign Secretary’s campaign is struggling with a series of polls putting her in last place among the five contenders to replace Jeremy Corbyn .
But speaking in her hometown of Guildford, Ms Thornberry said: “I’ve led the charge as Shadow Foreign Secretary against Donald Trump and the war in Yemen, and in the two years I shadowed Boris Johnson as Foreign Secretary, I showed him up every time for the lying, reckless charlatan that he is.”
In a bid to jumpstart her ailing campaign she said the party shouldn’t set ideological tests in the race for its next leader.
She said: “We must not make the mistake of defining it as a choice between who will take us to the left, or to the centre or to the right, because the only issue that really matters now is who will take us forward.”
Ms Thornberry warned that Labour faces “a long, tough road back to power” after the party suffered its worst general election defeat since 1935.
“In my 42 years as a member of the Labour Party, there is no fight or campaign our movement has waged where I have not been on the frontline.
“And since coming to Parliament 15 years ago, I’ve also been on the frontline in the fights against climate change, Universal Credit , and anti-abortion laws in Northern Ireland.”