Involvement in attack on ex-spy

no longer be ignored as scrutiny falls on wealthy Russians sheltering their assets in the UK drug trafficking, child pornography and mercenary organisations operating in the Ukraine.

Mr Blackford said the flow of money “must be stopped”. He said: “The UK government has acted as a roadblock to reforms in recent years. They prevented our attempts to introduce effective Magnitsky legislation, and blocked SNP amendments on tackling the use of SLPS to funnel millions of pounds in dirty money.

“We must take strong and robust action to protect our national security, and tackle these corrupt and criminal activities.”

Asked about the donation from Mrs Chernukhin –now a British citizen whose husband served under Mr Putin as a finance minister until 2004 – Mr Johnson admitted that he had played a tennis match in exchange for the £160,000.

Mrs Chernukhin is also understood to be the donor who paid £20,000 earlier this year to have dinner with Scottish Conservative leader Ruth Davidson. The dinner has not yet taken place.

Mr Johnson told the BBC’S Andrew Marr Show: “Unless and until evidence is produced against individual Russians, I do not think the entire nation should be calumnified.

“There are many Russians who have come to this country, made their lives here and contributed magnificently to our culture and our society. They feel threatened … it is very important that we do not allow a miasma of suspicion about all Russians in London.”

He added: “It is quite extraordinary at a time when you have two people lying gravely ill in hospital in Salisbury, when a police officer is still not out of hospital, for the fire somehow to be turned on Conservative Party funding. To the best of my knowledge all possible checks have been made and they will continue to be made.”

Labour said Mr Johnson and the Conservative Party had “serious questions to answer” about donations from sources linked to the Kremlin.

Shadow chancellor John Mcdonnell has suggested a package of measures to make up an “oligarch levy”, including new taxes on offshore property purchases and powers to confiscate illegal “unexplained wealth”.

Shadow Cabinet Office minister Jon Trickett said: “We know the Tories have taken more than £3m in Russianlinked donations since 2010, including £800,000 under Theresa May’s leadership, but we don’t know the nature of all those funds. The Conservative Party can’t remain silent any longer, the public have a right to know what checks if any they made to establish the source of all the wealth amassed by their donors.”

Conservative spokespeople have insisted all donations comply with electoral law.