Business Secretary Kwasi Kwarteng insisted it was “reasonable” for the prime minister to take a break, after he reportedly flew to Marbella to holiday in a private villa on the Costa del Sol.
Mr Kwarteng said he remains in “regular WhatsApp contact” with the prime minister, who he noted has recently lost his mother.
Downing Street did not deny reports Mr Johnson had travelled to Spain, but declined to say whether the prime minister was instead working at No 10 or in Chequers, as is commonplace.
Mr Johnson travelled with pregnant wife Carrie and their one-year-old son Wilf following the Conservative Party conference last week, according to the Mail on Sunday.
The Business Secretary told Times Radio: “I believe he has gone away. I’m not sure where he’s gone.
“But what I would say is I am in regular contact with him. He’s also had a year-and-a-half in which he’s almost lost his life to Covid, his mother passed away very sadly two or three weeks ago and he may have decided to take a short break.
“I think that’s something reasonable.
“I’m in regular WhatsApp contact with him, I spoke to him only a few days ago. I’m not sure when he’s supposed to have left the country.”
Labour called for “urgent answers on who exactly is running the show” after Mr Kwarteng’s claims he was in talks with the Treasury over support for firms struggling during the energy crisis were denied by the Treasury.
Shadow chief secretary Bridget Phillipson said: “In the teeth of a crisis of its own making, the Government has put its out of office on.
“The prime minister has gone on holiday, no one knows where the chancellor is, and this morning we understand the business secretary has entered the realms of fantasy.”
Holidays have at various times caused difficulties for Mr Johnson’s government.
Dominic Raab was demoted from his role as foreign secretary after criticism for staying on vacation in Crete while the Taliban marched back to power in Afghanistan.
The prime minister himself also endured months of scrutiny after a trip to the Caribbean island of Mustique in 2019.
He was ultimately cleared of breaking the MPs’ code of conduct after an investigation into whether he adequately registered £15,000 worth of accommodation paid for by a Tory donor.