Angela Eagle has given a strong hint that she wants to be Labour leader, telling Boris Johnson to “beware of the blonde bombshell”.
The Shadow Business Secretary, who is the most senior woman in Jeremy Corbyn’s team, made the joke as she repeatedly attacked the former Mayor of London on the ITV EU Debate on Thursday night.
Eagle went on the offensive against Johnson throughout the two-hour showdown, which was televised live in prime-time.
She hit back as the Tory MP and future leadership contender jibed that only the Tories had produced a female Prime Minister, Margaret Thatcher.
"Labour has still to produce a woman leader of the party...though maybe Angela Eagle will sort that out at some stage," Johnson said.
Eagle swiftly hit back: "Boris, beware of the blonde bombshell!"
Her remarks, which played on Johnson's own famous mop of hair, appeared to be a reference to both Tories underestimating Mrs Thatcher and to her own ability to take him on.
As well as Shadow Business Secretary, Eagle is also Shadow First Secretary of State and as such deputises for Corbyn at Prime Minister's Question Time.
She has impressed Labour MPs with her Commons performances and in the ITV debate became the most senior figure in the party to take part in a live EU debate.
In the debate, Eagle rounded on the Vote Leave claim that the UK sends £350m to Brussels every week, challenging Johnson to 'take that lie of your bus'.
But she also acted as Labour's main spokesperson urging the party's voters to back the Remain camp in the June 23 EU referendum.
Labour was founded to protect and create jobs, she said, and warned that Brexit was a big risk to workers' employment and rights.
After claims that Corbyn has failed to be passionate enough in campaigning for the Remain vote, and polls showing some voters weren't sure of Labour's position, Eagle went out of her way to speak for trade unionists and workers.
"We’ve got Boris Johnson pretending to be concerned about the problems of public services," she said.
"Boris Johnson voted with the Conservative government to have huge cuts to public services and that’s where a lot of this problem has come from."
Labour MPs have speculated that if there is a Brexit vote, Corbyn would face a swift leadership challenge if he was blamed for not doing enough to secure Labour's 30-year-old policy of backing the EU.
The last time the party wanted to pull out of the then EEC was in Labour's infamous 1983 general election manifesto, dubbed 'the longest suicide note in history'.
Although Eagle came fourth in the deputy leadership contest last year, she has plenty of union support and comes from the 'soft left' that now dominates much of the party. For some MPs, she is seen as a possible post-Corbyn leader, whenever he either stands down or is forced out.
And in her summing up, Eagle rammed home the jobs and employment rights she claimed would suffer from Britain quitting the EU.
“Listen to Britain’s trade unions and listen to the economic experts: they say leaving Europe will damage the economy, costs jobs... It won’t be Boris Johnson who suffers the consequences of a smaller economy...
“I have fought the Tories all my life, but this is not a referendum on the Government; it’s about the future of our country and the Labour party believes passionately that our future lies in Europe.”
On the ITV show, Eagle repeatedly jibed Johnson, at one point deploying a quote from Sir John Major that leaving the NHS in the hands of the Vote Leave camp was like leaving 'a pet hamster with a hungry python'.
Eagle also cited Dr Sarah Wollaston, the Tory MP and GP, who defected from the Brexit camp to the Remain camp in protest at claims that the £350m sent to Brussels could be spent on the NHS.
Fellow doctor and Tory MP Dr Philip Lee also came out in favour of the Remain camp on Thursday night.
Others watching the debate pointed out the problems with the Leave camp's claim, which has been disputed by the head of the UK's official statistics body.
In yet another attack directed at Johnson, Eagle also won applause for praising migrants who boosted the health service.
The Shadow Business Secretary also highlighted her own experience as a former minister, when she was part of the EU council of ministers who created the European Arrest Warrant that helped bring a 7/7 bomber to justice.
However, she did make one gaffe in the debate, confusing the visa-free Schengen area with the EU itself.
She said 'We are not in the European Union'. To which Johnson chipped in and said "Fantastic news!", to laughter from the studio audience.