Former defence secretary Sir Michael Fallon has urged ministers to consider spending at least 2.5% of GDP on defence by the end of this parliament, in response to the threat posed by Russia.
The senior Conservative MP said the incident in Salisbury had shown that "what Russia really understands is weakness".
He also said the Government should do more to combat fake news and publish intelligence more quickly to disprove Russian propaganda.
In a Commons debate on national security and Russia, Labour's Chris Bryant also hit out at the "bizarre" obsession of Vladimir Putin with homosexuality, given he was "a man who seems to like taking his shirt off more than any other political leader".
Sir Michael told MPs that while Britain met the Nato target to spend 2% of GDP on defence, Russia was spending more than 5%.
"In the last year of the last century, the Blair government was spending 2.7%," he added.
"That was before 9/11, that was before Daesh terrorism, that was before Kim (Jong Un) had his nuclear weapons. It was before cyber-attacks on our Parliament, and it was before Russia became more malignant again.
"I don't recall anybody, and I was in the House, in 1999 suggesting that our armed forces were overfunded then."
If Britain wanted to maintain its commitments around the world "then we have to will the means to do so", said Sir Michael.
He added: "We do now have to set our mind to a higher defence target, and I have said publicly that I think we should be committing, under the next spending review, to meeting at least 2.5% of GDP by the end of this parliament.
"If there is one thing that Salisbury has taught us all over again, is that what Russia really understands is weakness.
Countries that won't stand up for themselves, won't protect their people, won't protect their values and the freedoms that they enjoy.
"We've never been such a country. Salisbury should remind us all that we never should be."
Sir Michael also told ministers to "rise to the challenge of fake news" posed by hostile states.
"It is the speed with which Russia is able to do this, using propaganda, social media, the bots and all the rest of it, that require our response to be so much quicker," Sir Michael said.
"We need to deploy faster truth.
"I appreciate the difficulties of revealing or sharing intelligence. But where we have photographs of a mobile launcher that brought down an aircraft, where we know that an agent as powerful as Novichok could only be developed in the highest grade, most technically advanced state laboratory, then we need to get these facts out far, far more quickly."
He also called on Nato to refocus on the Russian threat and spoke out in support of a new security partnership with the EU after Brexit, alongside helping to end the reliance on Russian oil around Europe.
Mr Bryant, a former minister, said: "One of the things I find personally the most bizarre elements of the whole Putin charade is his personal and his regime's utter obsession with homosexuality.
"For a man who seems to like taking his shirt off more than any other political leader, this does strike me as phenomenally bizarre. I gather he also likes Abba. What can I say?"
Tom Tugendhat, Conservative chairman of the Foreign Affairs Select Committee, described comparisons of Russia and Nazism as "not accurate" - an apparent criticism of Foreign Secretary Boris Johnson.
He said: "Nazism was a hateful ideology that sought the death of millions, that deliberately sought to persecute and murder thousands and hundreds of thousands and millions of many - including Jews and gays and gypsies.
"We're not dealing with that in today's Russia, we're not dealing with an ideology, we're dealing with a kleptocracy, we're dealing with a simply thieving regime under the leadership of one man who has enriched himself beyond the dreams of Croesus or avarice."