The Commons voted last week not to review the 2003 Extradition Treaty under which McKinnon will be extradited to the US on hacking charges, despite the fact that all his crimes were committed in the UK.
"I believe it is the role of backbenchers to probe and criticise. In instances like the McKinnon case, which relate to people's rights and liberties as well as common sense, you should just spurn the diktats and the Whips," Mr MacKinlay told The Daily Mail.
"I was really frustrated by the vote last week. Many of my colleagues had expressed their sympathy for Gary McKinnon. But when the crunch came, they just went tribal and followed the diktats of the party. Their concept of parliament is totally different to mine."
Motions backing McKinnon's case had been signed by 74 Labour MPs, but only 10 voted for a review of the treaty during last night's vote, and the government comfortably defeated it by 290 votes to 236.
McKinnon now has only a High Court action to keep him in the country, which is due to be ruled on next week. His lawyers have said that his vulnerable condition - he has Asperger's Syndrome - would leave him at risk of suicide.
McKinnon freely admits that he illegally entered US military networks, but claims that any damage caused was accidental and that his primary purpose was to seek out information on alien life forms that he believed the government was suppressing.
"It's incredible, wonderful news and [Andrew MacKinlay] has my complete and total respect," McKinnon's mother, Janis Sharp, told the paper.
"I think it's tremendous that he has the strength to stand up and do what he believes is right. The way the MPs behaved was quite devastating for us. It's so refreshing to hear Mr MacKinlay's decision."