Marina Litvinenko’s husband, an outspoken critic of Vladimir Putin, died after drinking tea laced with radioactive polonium-210 in 2006.
A public inquiry a decade later concluded that his killing had “probably” been carried out with the approval of the Russian president.
Now his widow has spoken out about former SNP leader Mr Salmond’s controversial show on RT.
Ms Litvinenko said the former SNP leader’s decision to host a weekly show on the on the channel “can’t be excused”.
“You [Salmond] are doing this because you believe you might do good things, in a wrong place,” she told the Sunday Herald.
“It doesn’t work. My message is that I believe he is a people’s man, and everybody can make mistakes, but you need to think twice.
“It would be better to give it up, but it’s his own decision.”
She compared the former First Minister to former German chancellor Gerhard Schroeder who, after leaving office, worked for Russian energy firm Gazprom. She said: “Unfortunately, we have not only Schroeder, but we have other people now like Salmond, who is happy to work for Russian money.”
An RT spokesman said: “We sympathise with Marina Litvinenko in her loss and hope that she may find solace in this life that has treated her so cruelly.”
Mr Salmond’s decision to host a programme on the network has been criticised by opposition politicians as well as his successor as First Minister, Nicola Sturgeon, who said she would have “advised against RT and suggested he seek a different channel”.
The broadcaster has been accused of being a Kremlin propaganda machine, although it claims its journalists are independent.
Mr Salmond, who has been contacted for comment, has said he retains “full editorial control”.
Last week, Defence Secretary Gavin Williamson branded RT a “Russian propoganda channel” and advised MPs against appearing on it.
RT, formerly known as Russia Today, is being investigated by regulator Ofcom. Asked about MPs appearing on RT, Mr Williamson said: “I can’t understand why people would be wishing to go on what is effectively a Russian propaganda channel that’s obviously propagating the lines of the Kremlin. Ultimately people have to make their own choices, but it’s certainly not something that I would advise.”