British Prime Minister Theresa May came under sustained pressure over the Conservative Party's record on public sector pay, mental health services and social care during BBC1s Question Time broadcast less than a week before polling day.

May faced a string of awkward questions from members of the public on Friday, including a challenge from a nurse, Victoria Davey, who left the leader faltering after confronting her over the one per cent pay increase of NHS staff, the Guardian reported on Friday.

The British Prime Minister said she recognised the hard work people did in the health service but said her party had taken the difficult decision of enforcing pay restraint. 

May claimed wages in the NHS had increased, to which a man in the audience shouted that there had been a real-term salary drop of 14 per cent since 2010, adding: "So don't tell us we're getting a pay rise."

Under pressure after refusing to turn up for a TV debate earlier in the week, May rejected an accusation that she did a U-turn by calling a snap general election, the daily reported. 

Appearing after May on the programme, Labour leader Jeremy Corbyn also faced hostile questioning.

Pressed over his willingness to push the nuclear button in the face of an imminent threat, the Labour leader said: "I think the idea of anyone ever using a nuclear weapon anywhere in the world is utterly appalling and terrible… I would be actively engaged to ensure that danger didn't come about."

"There has to be no first use". 

Foreign Secretary Boris Johnson hit out at Corbyn later, saying: "There is no point in having a nuclear weapon unless you are willing in principle to deploy it." 

"I'm afraid there is a lesson here about Jeremy Corbyn's psychology and his politics and his naivety, with which he approaches not just the logic of the nuclear deterrent but also the Brexit negotiations."

In her session, May was asked why she was not able to provide details of the maximum amount of money people would have to spend on social care, which was only promised after days of backlash against the policy.

May defended her failure to set out additional details, even though the policy is blamed for reducing the Conservatives' lead in the polls in the past fortnight. 

She focused on Brexit and attacks on Labour over the question of leadership.

"I called a general election because I believe the British people have a right to vote and say who they want to see leading them through the Brexit process," she said. 

On the BBC1 programme, she hit out at Corbyn with her election mantra that he could only get into Downing Street "propped up by the Lib Dems and the Scottish Nationalists".