A former head of MI5 has hit out at a lack of “moral courage” among British politicians who failed to stand up to Vladimir Putin in the years before Russia’s invasion of Ukraine.

Lord Jonathan Evans the UK could have intervened to deter Russia earlier, but chose not to because it was easier to accept Russian money in London.

Speaking at an event hosted by the Royal United Services Institute in London, he said: “If you are an unconstrained autocrat and you take a risk and it pays off, then you think ‘Oh, good’.

“And then you take another risk, a bigger risk, and it pays off, and you think ‘I’m quite good at this, aren’t I?’.

“And then you take a bigger risk, and the world gets more and more dangerous. And that’s exactly what was happening with Putin.

“He started taking risks, and the West sat on its hands and did nothing about it, and he thought: ‘Oh well, that’s fine, I can take risks and they pay off’.”

Lord Evans, who led MI5 between 2007 and 2013, said that while the “moral fault” for the Ukraine war lay with Mr Putin and Russia, Britain could have done more to prevent it.

He said: “The opportunity was there at an earlier stage for us to have stepped in.

“But we chose not to because it was easy not to, and we liked donations from Russian oligarchs to our parties in London, and we liked going to their parties in London in another party sense.”

He added: “It was a complete lack of moral courage.”