Four people have been charged with leaking information from the Trump administration, the US attorney general announced on Friday, as he took an aggressive stand against the deluge of leaks that have plagued the first six months of the presidency.

Jeff Sessions, who was taunted by his boss, President Donald Trump, for being weak on leakers, said that he would leave no stone unturned in the hunt for the culprits.

His remarks came after the highly-damaging, and highly unusual, leak of transcripts of Mr Trump’s telephone calls with the leaders of Mexico and Australia.

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"No one is entitled to surreptitiously fight their battles in the media by revealing sensitive government information,” said Mr Sessions.

“No government can be effective when its leaders cannot discuss sensitive matters in confidence or to talk freely in confidence with foreign leaders."

Mr Sessions did not provide details of the four, besides confirming said they had been charged with unlawfully disclosing classified information or concealing contacts with foreign intelligence officers.

But, in his remarks at the justice department, he announced that his department has more than tripled the number of active leaks investigations compared to the number pending when President Barack Obama left office. He also said the department is reviewing guidelines related to subpoenas of journalists.

"This nation must end the culture of leaks,” he said, in remarks guaranteed to please his boss.

“We will investigate and seek to bring criminals to justice. We will not allow rogue anonymous sources with security clearances to sell out our country any longer.”

Kellyanne Conway, a White House adviser, on Friday morning even raised the possibility of using lie detector tests to root out leakers.

"It's easier to figure out who's leaking than the leakers may realise," she said.

Asked on Fox News if lie detectors may be used, she replied: "Well, they may, they may not."

Mr Sessions remarks came as the Russian election hacking investigation – the subject of many of the leaks – gathered pace.

America was on Friday digesting the implications of a decision by Robert Mueller, the special counsel, to appoint a grand jury to assist his investigation. The convening of a grand jury, a standard prosecution tool in criminal investigations, suggests that Mr Mueller and his team of investigators are likely to hear from witnesses and demand documents in the coming weeks and months.

Robert Mueller, the special counsel

It was also reported on Friday that two Republicans on the House intelligence committee travelled to London earlier this summer to speak to Christopher Steele, the British former intelligence officer behind the controversial dossier detailing some of Mr Trump’s alleged activities in Russia.

The two politicians left their addresses at two London addresses connected to Mr Steele, who worked for intelligence firm Fusion GPS, and chanced upon Mr Steele at his lawyer’s office, while he was there.

The Americans, following instructions from Washington, did not meet the former spy.

But their attempts to track down Mr Steele – without informing their Democrat colleagues, the Senate or Mr Mueller – have infuriated Washington investigators hoping to get to the bottom of the story.

“What is clear is that the president and his allies are desperately trying to smear Fusion GPS because it investigated Donald Trump's ties to Russia,” said Tracy Schmaler, a representative for Fusion GPS, in a statement.

Christopher Steele, the former MI6 agent who compiled the Trump dossier on behalf of his clients

Mr Trump on Thursday night was holding a “Make America Great Again” rally in West Virginia, where he repeatedly referred to the Russia investigation, which is evidently weighing on his mind. Earlier on Thursday it was reported that Mr Trump’s financial and business dealings were coming under Mr Mueller’s microscope – something that the president said in an interview with the New York Times was unacceptable.

“What in the world is wrong with us as people? Have we not heard enough about the Russians?” he said.

“The Russia story is a total fabrication. It's just an excuse for the greatest loss in the history of American politics. That's all it is. It just makes them feel better when they have nothing else to talk about.”

He then continued: “Most people know there were no Russians in our campaign. There never were. We didn't win because of Russia. We won because of you. That I can tell you.

“Have you seen any Russians in West Virginia or Ohio or Pennsylvania? Are there any Russians here tonight, any Russians?”