Labour MP Emily Thornberry has threatened to sue former colleague Caroline Flint who said the staunch Remainer had called Brexit voters “stupid”.

While Labour continues the autopsy of its election campaign after experiencing its worst loss since 1935, former Labour MP Caroline Flint said a significant factor was Labour Leavers rejecting the party’s anti-Brexit stance.

Ms Flint told Sophy Ridge on Sky News that 59 seats were lost because working-class voters in the heartlands felt isolated by elitists at the top of the party. She said: “In many respects, our party, in terms of the voices that are heard have gone too much towards the metropolitan cities and the university towns and away from these core areas.”

Name-checking Keir Starmer and Emily Thornberry, in particular, she said: “I don’t think anybody who have been architects of European policy can be a credible leader. I don’t think they can win back those seats… I don’t believe there’s any credibility with these people.

“Keir Starmer led us to a policy that didn’t listen to Labour Leave voices who urged caution. He led us down the path of a second referendum, and Emily Thornberry did as well. She said to one of my colleagues: ‘I am glad my constituents are not as stupid as yours.’ I’m sorry; it’s not acceptable.”

'I stand by my comments.' Former Labour MP Caroline Flint defends her criticism of Emily Thornberry, who she claims said 'my constituents aren't as stupid as yours.' pic.twitter.com/S2x9o9Xrc1 — Good Morning Britain (@GMB) December 16, 2019

It would not be the first time Thornberry — who as the wife of High Court Judge Sir Christopher Nugee holds the title of Lady Nugee — has come under fire for classism. In 2014, she resigned from the shadow cabinet after tweeting a picture of a terraced house in Rochester with a white van — popular with working-class tradesmen for their businesses — and St George’s flags flying from the windows.

The picture was taken to have been tweeted out of spite, and after a British newspaper tracked down the owner of the home and white van, he said of Thornberry: “I’ve not a clue who she is, but she’s a snob.”

Thornberry, the daughter of a former assistant secretary-general of the United Nations, has denied Ms Flint’s claims and has threatened to sue the former politician for “making up shit” about her. She told Sky News on Monday: “I’ve contacted her and I’ve said to her: please withdraw, I’ll give you until the end of the day. And she hasn’t. So I’ve had to go to solicitors.

“People can slag me off as long as it’s true; I can take it on the chin. But they can’t make up shit about me — and if they do, I have to take it to the courts.”

Ms Flint stood by her allegation on Monday, telling Piers Morgan on Good Morning Britain: “I made my comments yesterday. I stand by them [but] I may be subject to legal proceedings so I don’t think I should comment on it any further.”

Writing in The Guardian, Ms Flint also said the other major issue for Labour voters was Jeremy Corbyn himself. Not only did voters find his policies undeliverable — “free childcare, free tuition fees, free transport, free broadband” — they deeply disliked him.

The former Don Valley MP wrote: It’s not unusual in elections to hear voter dislike of our leader, but never on this scale. Voters made quite clear — sometimes brutally — what they thought of our candidate for prime minister.

“Occasionally we met someone who loved Jeremy. But after thousands of conversations, my party workers and I found the hostility to Jeremy relentless. Too leftwing, unpatriotic, against the armed forces, poor on TV, unwilling to say sorry for antisemitism, his handling of Brexit … the list went on.”

Mr Corbyn, who is due to step down as party leader in March 2020, claimed that even though Labour had not won the election, it had “won the argument”, saying: “There is no doubt that our policies are popular.”

Apparently having failed to learn any lessons from the disastrous election result, the present favourite to be the next Labour leader is described as a Corbyn “loyalist”, Rebecca Long-Bailey.