Today’s politicians are of “lower quality” than in previous years because of the “vile” treatment they receive, Sir Tony Blair’s former spokesman has said.

Alastair Campbell, an activist, author, journalist, podcaster and political strategist, said younger people are leaving the political sphere due to how harshly they are treated by voters.

Mr Campbell was then-prime minister Sir Tony’s official spokesman and Downing Street press secretary from 1997 and later became director of communications and strategy at No 10.

Speaking at a session during the Edinburgh Book Festival on Sunday, host Isabel Hardman, assistant editor of The Spectator, asked Mr Campbell if “good people” are still entering politics.

Mr Campbell, who is co-host of The Rest Is Politics podcast with former Conservative cabinet minister Rory Stewart, said he felt the current crop of politicians are generally of a lower standard because of the way they are treated by society.

Mr Campbell said: “Well, let’s be frank about it, there are people who have just been elected who will become prime minister.

“There are people who have just been elected who will become foreign secretary and home secretary and chancellor in the next whatever – on both sides – so there will be very, very good people there.

“I think in general, the quality is lower than it was, but again, I think we’ve all got to take ownership of that.

“I think one of the reasons is we are so vile to them.”

The author of But What Can I Do? gave the example of the attacks made on Labour minister Jess Phillips, the MP for Birmingham Yardley, who he said receives “so much abuse”, adding people have “got to be very tough to go into politics at the moment”.

Mr Campbell agreed with Ms Hardman that budding politicians “have to have a thick skin that is almost on the level of a rhino hide” in order to thrive.

“I agree. I’ve got a very, very thick skin. I put up with a lot of abuse, I get ‘war criminal’ every single day of my life on social media, very rarely to my face, but occasionally.

“And you do have to develop a thick skin, and you put your finger on it: developing your thick skin and remaining empathic to other people is hard, you have to think about how you do it.”

Mr Campbell said he met former SNP MP Mhairi Black, who had previously said the reason she did not stand for re-election was the “toxic” workplace environment at Westminster, on the night of the last General Election.

“I did Channel 4 on election night, and Mhairi Black was on, and I was thinking, ‘there’s Mhairi Black, she’s still very, very young and she’s given up politics’, right?

“She’s great. I mean, I’m Labour, she’s SNP, but I just think she had something really special. She’s given up.”

Mr Campbell said Ms Black, who was 20 when she was first elected in 2015 and is now 29, told him how unhappy she had been with how the Westminster Parliament operates.

He made a wider point that many younger people, often in their 30s or 40s, are leaving politics, adding “that can’t just be about them”.

“That’s about the experience that they’re having as politicians and that’s why I think we need to rebuild a sense of ‘they’re not as bad as we say’.

“Now, look, some of them are. It will be no secret to anybody who listens to my podcast or read anything I write, I despise Boris Johnson and what he did to this country.”

“I’ve never picked that up,” Ms Hardman joked, met with laughter from the audience.

Mr Campbell added: “I cannot stomach Donald Trump. Now there’s two people who’ve ended up running countries, but I don’t despise most politicians, and there are Tories that I can get on with.”

Mr Campbell’s book, But What Can I Do, is available online.