Labour has accused Boris Johnson of creating a “cash-for-access culture” in the Conservative party after it emerged that a secret advisory board of wealthy donors were regularly invited to private briefings with the prime minister and his top team.

Concerns were raised when the Sunday Times reported that members of the board, whose investments spanned property, construction and big tobacco, lobbied the government to provide more support for their businesses during the Covid crisis.

A witness was quoted by the paper saying that the donors believed their advice and the concerns “would go straight up to the PM”.

It was also claimed that board members were granted the contact details of ministers and advisers, which they used to discuss the pandemic strategy and procurement offers – as well as make requests for help and advice on applying for public appointments.

There were 12 figures named who had been invited to meetings since the Covid-19 crisis began in March 2020, including Lubov Chernukhin, a former banker who is the wife of Vladimir Putin’s former deputy finance minister Vladimir Chernukhin.

In total, the board members were said to have donated £22m to the Conservatives, including £9.9m since Johnson became prime minister less than two years ago.

The two figures central in putting the board together and maintaining its access were named by the Sunday Times as Lord Lister, Johnson’s former chief strategic adviser, and Ben Elliot, the Conservative party’s co-chair.

Lister and Elliot have been contacted for comment.

After the government promised a crackdown on money laundering from Russian oligarchs in light of the escalating military tensions in Ukraine, Labour accused the Conservatives of having “ignored warnings about how Russian money and influence is used in the UK”.

Anneliese Dodds, Labour’s chair, said the UK had become “a laundromat for kleptocrats’ dirty money” and that “our institutions have been damaged and an entire cottage industry has grown up dedicated to lobbying for and protecting those close to the Kremlin”.

In a letter to Johnson, which was seen by the Guardian, Dodds disparaged the “ethical standards in your party” and said the media report over the weekend “raises serious questions about the cash for access culture that you have created at the heart of government”.

Dodds said Johnson had allowed Elliot to “blur the lines between private business activities and his public responsibilities in order to boost Tory coffers”.

Given concerns about the source of the money donated to the Conservative party, Dodds said Johnson should “return every penny of the millions of pounds of Russian-linked cash that has been donated to your party and its MPs since 2019 – including any received from advisory board donors – and reverse your plans to allow unlimited donations from abroad”.

Dodds also called for Elliot to be fired and told Johnson he should get his “own house in order and restore public confidence that your party is committed to cleaning up its act”.

Downing Street and the Conservative party were contacted for comment.

A spokesperson for the Conservatives told the Sunday Times: “We can confirm that, on occasion, senior Conservative politicians, just like senior Labour and Liberal Democrat politicians, do in fact attempt to raise funds for the party they represent.”