A Conservative peer who chairs a firm being sanctioned in the US for its Russian links has declined to give public evidence about it to a parliamentary committee, leaked documents disclose.

Lord Barker of Battle, the chair of the aluminium giant EN+ which is majority-owned by Russian oligarch Oleg Deripaska, did not wish to appear in open session before MPs because he hopes to persuade Washington to lift the sanctions, letters show.

Sanctions were imposed on Deripaska and EN+ in April because of the oligarch’s close relationship with the Russian president, Vladimir Putin. The letters from Barker are due to be discussed by the foreign affairs select committee, which is looking into the flow of Russian money into the UK, on Wednesday.

The disclosure will raise concerns that the peer is being allowed to avoid parliamentary scrutiny. A Whitehall source said it was “highly unusual” for a parliamentarian not to give public evidence to a committee.

The letters also detail Barker’s attempts to persuade the US authorities to lift sanctions against EN+.

In April, the US treasury imposed sanctions on the company – whose assets include a stake in Rusal, the world’s second-largest aluminium producer – over what it called the Kremlin’s “malign activities”. Overall, it acted against seven oligarchs, 12 companies they own or control, as well as 17 senior Russian government officials amid allegations of Russian meddling in the 2016 presidential election and other issues. Deripaska resigned from EN+’s board in May but remains its biggest shareholder.

MPs are examining the issue of Russian money flowing into the UK following the nerve agent attack in Salisbury in March, which has been blamed upon the Kremlin, a charge it denies.

In a letter sent this week to the committee’s Tory chairman, Tom Tugendhat, Barker wrote that in light of sanctions against Deripaska, he is leading “a major effort” to take control of the company and would only give private evidence until negotiations with the US authorities have concluded.

“OFAC, the sanctions unit in the US treasury, has made it crystal clear that if certain changes are made to Deripaska’s controlling interest in the company, they are prepared to consider lifting the sanctions on the EN+ and Rusal group,” Barker wrote.

He said he would address MPs but only if the meeting was conducted in private. “Until this process is concluded, these measures remain financially and commercially sensitive. Nonetheless, given your interest in this area, I have offered your committee a confidential briefing in respect of this plan and my ongoing high-level discussions with the US treasury.

“You have declined that offer but I will be happy to return instead, as I have already informed you, once my discussions have concluded for an open public session,” he wrote.

In the letter, Barker also discloses that he offered to brief the security minister, Ben Wallace, about the US sanctions regime imposed on the firm and Deripaska.

However, he has denied allegations in the Times that he attempted to lobby Wallace.

Barker wrote: “I was very surprised to read this week in the Times, a leaked and partial extract of your correspondence with the minister that suggested that I had written to Mr Wallace ‘to request assistance for Russian associates’.

“As you know and as the attached letter makes absolutely clear, this is factually incorrect.

“I have written to Mr Wallace to kindly ask him to clarify the record and would be most grateful if you could also correct any false impression,” he wrote.

As supporting evidence to the committee, Barker included a letter he sent to Wallace in June in which he offered to meet the minister to explain how the firm planned to reduce Deripaska’s holding.

Barker, a former energy minister who has also been employed by Roman Abramovich, addressed the letter to “Dear Ben” and wrote: “I am now actively pursuing a number of radical changes in response to the imposition of US sanctions, details of which I would like to share with you.

“Together, these measures will result in the removal of Oleg Deripaska from the company and I am working closely with both the US administration, UK regulators and our minority shareholders to achieve this goal.

“Although I have no ask of you or any parliamentary colleague, I would be most grateful for an opportunity to come and update you on my progress and answer any questions you may have,” Barker wrote.

A source close to Barker said: “He wants to give a full account of himself but he cannot do that while negotiations are ongoing with Washington. Greg would be very happy to appear before the committee once negotiations have been concluded.”