Theresa May has compared herself to Liverpool football club in predicting she could make a remarkable comeback on Brexit even though Europe is winning and the clock is ticking.

In what appeared to be a scripted gag, she countered a suggestion from the Labour leader, Jeremy Corbyn, that she could learn how to do well in Europe from Liverpool. The football team defeated Barcelona 4-3 in the Champions League semi-final after trailing 3-0 in the first leg.

Corbyn paid tribute to Manchester City for their Women’s FA Cup triumph before joking: “In view of the amazing performance of Liverpool last night, perhaps the prime minister could take some tips from Jürgen Klopp on how to get a good result in Europe.”

May’s future is hanging in the balance as Conservative MPs are pressing her to set out a timetable for her departure as prime minister, whether or not she has secured a withdrawal deal.

But in remarks that suggest she still wants to achieve a Brexit deal before quitting, May said: “I actually think that when we look at the Liverpool win over Barcelona last night, what it shows is that when everyone says it’s all over, that your European opposition have got you beat, the clock is ticking down, it’s time to concede defeat, actually we can still secure success if everyone comes together.”

May’s green benches were notably emptier than usual at prime minister’s questions, a sign that backbench support for her leadership is ebbing away.

The two leaders sparred on the issue of falling numbers of the NHS workforce, after a staff survey found that 40% have reported suffering work-related stress in the last year alone.

Corbyn said the government’s failures were taking their toll on the NHS. He added: “Can the government explain why they have been so severely let down by this government?”

The prime minister acknowledged that “for too long, governments have failed to produce the proper workforce planning to give our staff in the NHS the care that they deserve”.

But she added: “It is this government with its long-term plan that is ensuring we are giving that care to staff.”