Energy secretary Amber Rudd led the charge as the Remain campaign launched a series of personal attacks on Boris Johnson in ITV’s Brexit debate.

Rudd lined up alongside SNP leader Nicola Sturgeon and Labour MP Angela Eagle to put the case for staying in the European Union.

Arguing for Brexit were Johnson, Tory minister Andrea Leadsom and Labour’s Gisela Stuart. But it was Johnson who was repeatedly duffed up by his opponents.

Rudd, a close ally of George Osborne, began in combative fashion when she responded to a question on immigration numbers by contending: “I fear that the only number Boris is interested in is Number 10.”

Sturgeon doubled down on the personal attacks, claiming: “Boris is only interested in David Cameron’s job.”

The SNP leader also questioned Johnson’s commitment to improving the health service: “I wouldn’t trust Boris Johnson on the NHS as far as I could throw him.”

Eagle seized on Vote Leave’s highly controversial claim the UK hands Brussels £350 million a week and directly implored Johnson: “Take that lie off the side of your bus.”

But it was Rudd who left the most damning assassination of Johnson to the end of the show. As she was summing up, the energy secretary said:

“What we’ve heard is complete fantasy from the Vote Leave team. It reminds me of the Wizard of Oz - when you pull back the curtain, there is nothing there.”

She then twisted the knife into her Tory colleague: “From Boris, well, he’s the life and soul of the party but he’s not the man you want driving you home at the end of the evening.”

For his part, Johnson concluded by insisting that the Britain would only be driven in the wrong direction if the country voted to remain in the EU.

He said: “They say that we have absolutely no choice but to stay locked in the back of the EU car, driven in the wrong direction going in a direction we do not want to go; we say we can take back control.”

Rudd's overall performance prompted some Westminster insiders to suggest that she, rather than Johnson, would be the next Tory leader - even though the energy secretary recently told a press gallery lunch [5] that she would not be throwing her hat into the ring.

But Rudd also provoked a backlash from her opponents, including fellow Tory MP Nadine Dorries who accused her colleague of demeaning the debate. Other Tory sources suggested that Rudd was acting on the orders of the chancellor.