A SENIOR US Democrat is seeking documents from the National Rifle Association (NRA) and the treasury department following reports of an FBI investigation into whether a Russian central banker funnelled money to the gun lobbying group during the 2016 presidential campaign.

In letters sent to Treasury Secretary Steven Mnuchin and the NRA, Senator Ron Wyden of Oregon requested any documents showing financial links between Russia and the group.

News reports last month said the FBI is investigating contact between Alexander Torshin, who is the deputy governor of Russia’s central bank and a close ally of President Vladimir Putin, and the NRA.

Wyden is ranking member of the senate finance committee, as well as a member of the senate intelligence committee, which is conducting a probe into Russian election meddling.

The senator wrote: “The national security as well as legal implications of these reports make it imperative that Congress conduct a thorough investigation.”

A separate letter addressed to NRA treasurer Wilson Phillips Jr included a more specific request for documents that detail financial transactions with Russian nationals.

Wyden wrote: “I am specifically troubled by the possibility that Russian-backed shell companies or intermediaries may have circumvented laws designed to prohibit foreign meddling in our elections.”

The letter cited a story on the FBI investigation published by McClatchy last month. The NRA, one of the most powerful lobbying groups in US politics, spent heavily to support Donald Trump’s presidential candidacy.

Trump strongly backed gun rights. Torshin, who is a lifetime member of the NRA, reportedly met Donald Trump Jr during an NRA gala in 2016.

As a member of the senate intelligence committee, Wyden is part of one of three congressional committees carrying out investigations into Russian meddling in the 2016 campaign.

But as a member of the minority party, he holds less sway in forcing the treasury department or an independent organisation like the NRA to produce documents.

Meanwhile, the White House has declassified a memo written by members of the Republican party on the Russian collusion probe.

This cleared the way for the US House intelligence committee to release the document, which is based on classified information and alleges the FBI abused US government surveillance powers during its investigation.

US president Donald Trump said “a lot of people should be ashamed of themselves” over the contents of the memo.

The president cleared the way for publication of the controversial document despite strong objections from the FBI, who said it could damage national security and mislead the public.

The four-page memo was drafted by Republicans on the committee chaired by congressman Devin Nunes of California.

Trump has accused the FBI and the justice department of bias over the Russian election meddling probe, claiming they had politicised “the sacred investigative process”.

The president tweeted: “The top Leadership and Investigators of the FBI and the Justice Department have politicized the sacred investigative process in favor of Democrats and against Republicans – something which would have been unthinkable just a short time ago. Rank & File are great people!”

Trump has told advisers he believes the document validates his concerns that the FBI and DOJ conspired against him.