Donald Trump has denied working for Russia and concealing his conversations with President Vladimir Putin from US officials.

In an interview with Fox News, Mr Trump claimed he was “tougher” on Russia that any recent US president and lashed out at the idea of collusion with the country as a “hoax” and a “witch hunt”. A number of senior Democrats have said that the reports raise “serious questions” about the president’s relationship with the Russian leader.

The president’s latest Russia-related tirade follows a report in The New York Times that the FBI opened a counterintelligence investigation in 2017 into whether the US president was actively working for Moscow. The investigation was said to have been launched after Mr Trump fired then-FBI director James Comey out of concern the president’s actions may have presented a threat to national security.

And according to The Washington Post, Mr Trump has gone to “extraordinary lengths” to hide details of his conversations with Mr Putin, including removing notes from his interpreter.

As part of an astonishing outburst over the reports, the president urged prosecutors to look into the finances of his former lawyer Michael Cohen’s father-in-law.

Mr Trump said his former fixer, who provided prosecutors with information about the Trump campaign before he was found guilty of financial crimes, should “give information on his father-in-law. That’s the one people want to look at.”

“I think it’s the most insulting thing I’ve ever been asked,” Mr Trump said of the story about the FBI’s national security probe. “I think it’s the most insulting article I’ve ever had written … Obviously nothing was found.”

Mr Comey was leading an investigation into Russia’s alleged interference in the 2016 presidential election at the time. US intelligence agencies have said Moscow tried to tip the election towards Mr Trump, something Russia has denied. The New York Times reported the counterintelligence probe was sparked in part by growing alarm about Trump’s behaviour, including comments he made suggesting he fired Mr Comey over the Russia investigation, which is now being led by special counsel Robert Mueller.

“If you ask the folks in Russia I’ve been tougher on Russia than anybody else,” Mr Trump said. “And probably any other president, period, but certainly the last three or four presidents.”

Mr Trump’s claim was disputed by Virginia Senator Mark Warner, the top Democrat on the chamber’s intelligence committee. He told CNN that almost all the sanctions on Russia arose not in the White House but in congress, due to concerns by members of both parties about Moscow’s election meddling and other actions. Mr Warner accused the White House of being very slow to put in place the penalties.

Unnamed US officials revealed to The Washington Post that there are no detailed records from any of Mr Trump’s five face-to-face meetings with Vladimir Putin over the past two years.

“I’m not keeping anything under wraps,” the president insisted. “I couldn’t care less. I mean it’s so ridiculous, these people make it up. The Washington Post – that’s basically the lobbyist for Amazon.”

The DC-based paper is owned by Jeff Bezos, the founder of the online marketplace giant.

He added: “I’m going through all this nonsense – it’s all nonsense, but I have to be careful because these are dirty players. You got the Mueller investigation, you got all this nonsense and there’s no collusion, no nothing.”

Senior Democrats said the report underscored the need for legislation to protect Mr Mueller’s probe.

“When he takes the interpreter’s notes and wants to destroy them so no one can see what was said ... it raises serious questions about the relationship between this president and Putin,” Dick Durbin, the Senate minority whip, said on ABC’s This Week.

“I do think it’s curious that throughout that whole summer when these investigations started, you had Vladimir Putin’s policies almost being parroted by Donald Trump,” Mr Warner told CNN’s State of the Union.

“I would need a firm commitment that he will not allow any interference in the Mueller investigation,” Senator Chris Coons, a Democratic member of the judiciary committee, said on Fox News Sunday.

The Republican head of the Senate Judiciary Committee said he plans to ask the FBI about the probe report, suggesting the agency may have gone too far.

“I am going to ask the FBI director – was there a counterintelligence investigation opened up regarding the president as being a potential agent of the Russians? I find it astonishing,” Senator Lindsey Graham also told Fox News.

“If this really did happen, congress needs to know about it,” he added. “How could the FBI do that? What kinds of checks and balances are there?”

White House press secretary Sarah Huckabee Sanders responded to the story about Mr Trump’s conversations with Mr Putin by saying: “The liberal media has wasted two years trying to manufacture a fake collusion scandal instead of reporting the fact that ... President Trump has actually been tough on Russia.”

Bizarrely, Mr Trump also told Fox News he hadn’t “left the White House for months”, even though he went to Texas on Thursday to make the case for his border wall and also travelled to Iraq in December.

On the planned border wall along the southern border with Mexico – the cause of the ongoing government shutdown after Mr Trump’s request for $5.7bn in funds to build it – the president said he could still declare a national emergency over what he has called an immigration “crisis”. That would allow Mr Trump to appropriate funds for the wall without congressional approval.

Democrats have offered $1.3bn in general border security funding, but no direct money for the wall. They have accused Mr Trump of throwing a “temper tantrum” over the wall and called on him to open the government.

“I have the absolute right to call a national emergency. I’d rather see the Democrats come back from their vacation and act,” Mr Trump said.