On the evening of 18 February, ten hours after announcing his resignation from the Labour Party, Chris Leslie MP is watching Parliament TV and trying to determine whether he needs to vote. “There’s an infrastructure to politics that you take for granted,” he observes in reference to the Independent Group’s lack of a whipping operation.

When Leslie returns from voting, he wryly remarks: “On this particular occasion we did vote alongside Labour!” (In opposition to the Brexit financial services bill.) Leslie, 46, who entered parliament in 1997 at the age of 24, becoming the “Baby of the House”, was a Labour MP for 17 years (for Shipley and then Nottingham East) and briefly served as shadow chancellor in 2015 during Harriet Harman’s acting leadership of the party.

It was Labour’s refusal to back a second Brexit referendum (while insisting that “all options are on the table”) that ultimately persuaded Leslie to leave the party. “We’ve been played for fools, it’s a very transparent bit of game-playing,” he says when we meet in the parliamentary office of his fellow splitter Chuka Umunna (whose mantelpiece features photos of him with centrist icons Emmanuel Macron and Justin Trudeau).

The Independent Group’s launch day did not pass without incident. Angela Smith, one of the original seven rebel MPs, referred during a BBC interview to people from ethnic minority backgrounds as having a “funny tinge”. When I raise the remark, Leslie replies: “I think she’s apologised… it’s clear that it was something misspoken rather than with malign intent.” He adds: “This is the way it’s going to be: we’re going to be under a lot of scrutiny. We’ve got a lot of big enemies with vested interests trying to shoot us down at every opportunity.”

Of the seven Independent Group MPs, Leslie’s presence was among the least surprising. He has long been one of Jeremy Corbyn’s most enthusiastically vociferous critics. At the group’s Westminster press conference, Leslie declared that Labour had been “hijacked by the machine politics of the hard left”.

Is this not another way of saying that Corbyn was twice democratically elected leader? “There was a massive recruitment into the Labour Party at a key moment of despondency,” Leslie says. “There was a regression into ‘ideological purity’, which of course is a great recruiting sergeant.” He insists that MPs should have the final say on a party’s leadership. “Everybody has genuflected to membership, but that membership is a tiny fraction of the public at large… MPs have to, by the nature of our constitution, have confidence in their leader.”

Leslie defends on similar grounds his refusal to trigger a by-election and seek the judgement of his constituents. “The individual representative is there to use their integrity and their judgement, they’re not just a delegate from a party list.”

His hope is that the Independent Group will evolve into a fully fledged new party and attract more defectors from across the House of Commons. “You won’t know unless you try… the challenge is cutting through the cartel of the old parties who act as if they own and can carve up cities and constituencies between themselves.” Though the left has publicly celebrated Leslie’s departure as a chance to select a socialist candidate (the MP was already facing possible deselection by his local party), he insists that Labour should be fearful. “They’re massively underestimating public opinion. I think they have become lazy and complacent about ‘their vote’ as they perceive it. Those who say ‘you’re splitting Labour’s vote’ are making an awfully big assumption about who it belongs to.”

Leslie does not dispute that many of the left’s policies are popular with the public: rather he questions their desirability. Of the renationalisation of the privatised utilities, he remarks: “It speaks to the controlling instinct of the hard left because there is a sort of view that John McDonnell sitting in the Treasury can mandate how many tractors are sold, or what trains should leave Euston at what particular time of day, or what should be the price of a stamp. The problem with the Marxist ideology is that it assumes this omniscience on behalf of the central controller.”

He is similarly sceptical of Labour policies such as a 50 per cent top income tax rate (“it depends on the use of that revenue and the economic impact”) and the complete abolition of university tuition fees (“sounds great, the minor problem is: how do you pay for it?”).

What, other than Brexit, does he disagree on with Theresa May’s Conservatives? “I think there are real problems with their welfare policies, which have had a tin ear to the most vulnerable in society. On housing it’s been lamentable, assuming that the market will purely deliver.”

Leslie does not disguise the anguish he feels at his decision (“It’s like a political bereavement”). Would he return to Labour under a different leader? “No, it’s not about Corbyn, I think this is a systemic problem and an ideological problem… I can see Diane Abbott there [gestures to TV] talking on behalf of the nation’s security, John McDonnell’s stewardship of the economy. Who knows? Chris Williamson might be special representative to the UN Security Council, perhaps Len McCluskey as governor of the Bank of England.”

If forced to choose, would he rather have May or Corbyn as prime minister? “They’re pretty much both bad options. I think it’s time to strike out and do our own thing.”