William Browder is the CEO and co-founder of investment fund Hermitage Capital Management, which was once the largest foreign investor in Russia. His accusations of Russian corruption have seen him barred from the country and tried in absentia for tax evasion. He is the author of "Red Notice: A True Story of High Finance, Murder, and One Man's Fight for Justice". The views expressed in this article are solely his.

(CNN) Alexander Litvinenko wasn't the first critic of Vladimir Putin to end up dead, and he won't be the last.

In March 2003 -- three years before the former Russian spy was poisoned in a London hotel -- the Kremlin issued a directive that authorized the assassination of individuals living abroad who were deemed to be "enemies of the state," according to a secret document posted on the website of the UK public inquiry into Litvinenko's death.

Since then, a number of Kremlin critics have died in mysterious circumstances around the world -- several of them on British soil.

The UK government's reaction to the murder of Litvinenko in 2006 was shockingly insufficient. Britain expelled four Russian diplomats and suspended ties with the Russian security services, which resumed again during the Sochi Winter Olympics.

Most shockingly, Home Secretary Theresa May desperately tried to block a government inquiry into Litvinenko's killing because, in her view, it would harm diplomatic relations with Russia. And a public inquiry only took place because of a British High Court ruling overriding May's attempts to silence the whole affair.

When you consider the circumstances of Litvinenko's murder -- his tea spiked with radioactive polonium-210 in a Mayfair hotel during a meeting with two former Russian security servicemen — this shamefully deficient reaction of the UK government put public safety at risk.

The victims of this crime were not just Litvinenko and his family. Traces of polonium-210 were found across London -- including at the Millenium Hotel, the Emirates football stadium, an Itsu sushi restaurant, and two planes at Heathrow airport. Approximately 700 people were tested for radioactive poisoning.

The Russian government had effectively carried out a mini nuclear attack on Britain, without consequence. In the mind of Vladimir Putin, British inaction signaled to Russian government assassins that they could get away with murder on UK soil.

I don't say this idly. In November 2012, a Russian whistle-blower named Alexander Perepilichnyy was in the process of giving evidence in a Swiss money laundering investigation -- exposing the beneficiaries of a massive fraud committed by Russian government officials -- when he collapsed and died while on a jog outside his home in Surrey, England. He was 44 years old and in good health.

While the Surrey police initially refused to investigate his death as a murder, the presence of a toxin was later found in his stomach, and the current inquest -- which my firm is involved with -- is ongoing.

Unless Britain wants to invite more murders on UK soil, the government needs to react.

When my Russian lawyer Sergei Magnitsky was murdered after uncovering a $230 million tax fraud in Russia, the U.S. government responded with the Magnitsky Act -- a 21st century law which bans killers, torturers and kleptocrats from entering the U.S. and using its financial system.

But although the UK Parliament has endorsed a similar bill in Britain -- one that I initiated and advocated on behalf of -- the UK government has refused to act.

Whose interests are they really protecting? It seems the government's desire to do business with Russia and maintain courteous diplomatic relations is more important than public safety and criminal justice.

British citizens are being used as testing fodder for the Kremlin's latest assassination methods, on British soil, and the government is doing nothing about it.

Today the UK's public inquiry has found that Litvinenko's murder was "probably approved" by Vladimir Putin and Nikolai Patrushev, the head of Russia's spy service at the time. Russia's foreign ministry has dismissed the inquiry as politically motivated, and Patrushev said "the charges against me are nonsense."

As a result of today's report , Putin and Patrushev should be sanctioned along with other members of the Russian President's inner circle.

Unless the government takes real steps to prevent Russian state-sanctioned killings -- including visa bans and asset freezes -- similar murders against Russia's "enemies" will continue to take place in the UK.

And next time, the innocent bystanders may not be so lucky.