David Cameron
Britain's Prime Minister David Cameron listens to a question during a news conference at Number 10 Downing Street in London on March 14, 2013. Reuters/Nick Ansell

British Prime Minister David Cameron raised the prospect of new European Union sanctions against Russia for its possible involvement in the Malaysia Airlines MH17 crash, saying the West must change its approach unless Moscow stops meddling in Ukraine.

Writing in The Sunday Times, Cameron said Russia "can use this moment to find a path out of this festering, dangerous crisis. I hope it will do so. But if that does not happen then we must respond robustly.”

"If President Putin does not change his approach on Ukraine, then Europe and the West must fundamentally change our approach to Russia,” he wrote.

He also said if independent investigators confirm MH17, carrying 298 people, was shot by a missile fired from an area held by pro-Russian separatists in Ukraine, then Moscow should be blamed for destabilizing the country.

"If it is the case, then we must be clear what it means: This is a direct result of Russia destabilizing a sovereign state, violating its territorial integrity, backing thuggish militias, and training and arming them," Cameron wrote. "We must turn this moment of outrage into a moment of action, action to find those who committed this crime and bring them to justice.”

The minister criticized fellow members of the EU for reacting too slowly to Russia and not facing up to the implications of what is happening in Ukraine.

Meanwhile, U.K. Defense Minister Michael Fallon accused Russia of sponsoring terrorism in Ukraine and warned Russian President Vladimir Putin to get out of the former soviet republic.

“It is sponsored terrorism as far as people of east Ukraine are concerned,” Fallon told The Daily Mail Sunday. “We don't know if somebody said: 'Let's bring down a civil airliner, wherever it's from,' but we need to find out."