Brexit news: Boris Johnson falls behind Jeremy Hunt in poll of British voters' preferred PM, amid Trump-esque hustings claim and no-deal hint

Mr Putin said in a recent interview that the Salisbury poisoning attack was "not worth five kopeks" (a fraction of a penny).

“Listen, all this fuss about spies and counterspies, it is not worth serious interstate relations," he told the Financial Times. "This spy story, as we say, it is not worth five kopeks. Or even five pounds, for that matter."

Asked about the attack, Mr Putin said: “Treason is the gravest crime possible and traitors must be punished. I am not saying that the Salisbury incident is the way to do it. Not at all. But traitors must be punished.”

Russia does not allow the extradition of its citizens but Ms May pledged to bring two suspects to justice "as soon as they set foot outside" the country.

Ahead of the talks, Mrs May defended her decision to meet Mr Putin.

"It's not business as usual and it can't be business as usual with Russia until they stop the sort of acts we have seen them doing around the world," she said.

"We in the UK have seen the use of a nerve agent, a chemical weapon, on the streets of Salisbury.

"We see other Russian activity around the world, we see the use of disinformation, cyber attacks and we need to see Russia desisting from that activity."

Mrs May told reporters that the meeting gave her the chance to deliver a "very clear message, leader to leader".

Boris Johnson has not responded to reports that he called the French "turds" over Brexit while he was foreign secretary.

He is said to have made the comment while being filmed for a BBC fly-on-the-wall documentary "Inside the Foreign Office".

However the insult did not feature in the three-part programme when it was aired last year. The remark was removed at the request of the Foreign Office, after a Whitehall memo suggested the comment would adversely affect relations with close ally Emmanuel Macron.

In another signal to party members that he is prepared for a no-deal Brexit, Mr Johnson's campaign team have revealed their plans for a an "emergency budget" in September.

The proposals include tax cuts, abolishing stamp duty on homes worth less than £500,000 and a "Trump-style" block on new regulations.

Mr Johnson has already promised to raise the threshold for the 40 per cent income tax rate from £50,000 to £80,000 - which is estimated to cost the treasury £9.6 billion.

He may also adopt Dominic Raab's plan to increase the national insurance contribution to £12,500, according to reports.

Former leadership rival Sajid Javid is being lined up for the job of chancellor, it is claimed.

The prime minister was determined to put on a grim face when she met Vladimir Putin for talks at the G20, having said she would demand the Russian president hand over the two prime suspects in the Salisbury poisoning attack.

Here's political editor Andrew Woodcock's report on Mr Putin's dismissal of the spy row ahead of the talks in Japan.

Boris Johnson and Jeremy Hunt will appear at another hustings today, in Exeter.

Iain Dale, who chaired the first debate, has called for "sensible" suggestions about questions to ask the candidates.

Jeremy Hunt managed to attack Jeremy Corbyn and Vladimir Putin in a single tweet as he prepared for the fourth hustings with party members.

Responding to Mr Putin's claim that liberalism was "obsolete" and multiculturalism was "no longer tenable", Mr Hunt said:  "This just shows what we’re up against. Corbyn at home, and people trying to subvert our values from abroad. Our democratic system based on rules, respect for individual rights & human dignity has created more happiness & wealth than any other way of life anywhere in the world."

The scene at the hustings in Exeter. While some photographs showed a long queue of members to get into the event, there are still some seats empty at the back. Others have described it as "packed".

Downing Street has said in a statement that Theresa May told Vladimir Putin at the G20 talks that the relationship between the two countries cannot be normalised until Russia stops its "irresponsible and destabilising activity".

The use of a deadly nerve agent on the streets of Salisbury formed part of a wider pattern of unacceptable behaviour and was a truly despicable act that led to the death of a British citizen, Dawn Sturgess.

She was clear that the UK has irrefutable evidence that Russia was behind the attack - based on painstaking investigations and co-operation with our allies.

She said that this behaviour could never be repeated and that the UK wants to see the two individuals responsible brought to justice.

The Prime Minister underlined that we remain open to different relationship, but for that to happen the Russian government must choose a different path.

The Prime Minister said the UK would continue to unequivocally defend liberal democracy and protect the human rights and equality of all groups, including LGBT people.