Republican leaders have moved to quash speculation about Mitch McConnell, the former Republican leader in the US Senate, amid a growing revolt over the lack of transparency around his health.

The 84-year-old Kentucky politician, who led Senate Republicans for longer than anyone in history before stepping down last year, was admitted to the hospital on 14 June but his office declined to say what he was being treated for.

The secrecy led to a backlash from Donald Trump’s support base, with some claiming that McConnell’s condition is graver than acknowledged and accusing his office of a cover-up.

On Tuesday, John Thune, McConnell’s successor as Republican leader, sought to quell the anger by claiming that he had spoken by phone with McConnell on Monday. A Thune spokesperson said: “They had a lengthy and substantive conversation that covered a variety of topics, including national security.”