It is hot and stuffy inside Ann Coffey’s Westminster office and the MP has been talking non-stop for 70 minutes without any sign of flagging. That’s quite surprising because Coffey, who recently quit Labour for the newly created Independent Group (which has applied to become a political party called Change UK) is not fizzing with vote-catching proposals.

She is the spokeswoman for children and education, but if she were to become education secretary tomorrow, she would not change the system. This is not simply because the Independent Group is still figuring out its policies: Coffey makes it clear she has little appetite for education reform in England. “I spend a lot of time visiting schools ... and what most people want is a system that is stable. We don’t want a system that when a new secretary of state wants to make their mark, they come up with a new initiative.”

The former social worker has represented the constituency of Stockport for 27 years, and increased her majority by 4,416 to 14,477 as the sitting Labour MP at the last election. She used to be parliamentary private secretary to Tony Blair and says she was heavily involved in setting up Sure Start centres under the Labour government.

Best known in recent years for being the chair of the all-party parliamentary group for runaway and missing children and adults, she has campaigned extensively against the criminal exploitation of children.

Coffey trained as a teacher – she thought it would be “a very stable job” – but gave up on the idea after a placement in a Birmingham secondary modern. “I questioned whether it was the best occupation for me.” On grammar schools, she says: “I personally find [them] difficult to justify.” But rather like former education secretary Ed Balls, she is in favour of local communities deciding for themselves whether to have selective schools. “What we’re very interested in doing is devolving decision-making to local areas,” she says. It sounds like the status quo.

She likes the idea, though, put forward to her by a parent, of forcing local authorities to justify how it is in a community’s interest to allow selective schooling, and to demonstrate the outcome it delivers. “And maybe that could be challengeable in court ... a bit like the judicial review process, except made more powerful.”

Coffey is aware of the Independent Group’s “centrist” label, but is critical of New Labour’s spending on education under Blair. “Sometimes I think that there’s an idea in the Labour party that public funding will sort it out. That what you do is you just spend money. And spending money is very helpful, but we spent a lot of money during the Blair years. It didn’t necessarily make the changes we wanted it to make because we didn’t necessarily invest it in where it should have been invested.”

The Independent Group at a press conference on 20 February 2019. Ann Coffey is second from the right. Photograph: George Cracknell Wright/Rex/Shutterstock

In February, when she left Labour after 41 years, she argued its current leadership had changed the party beyond all recognition, and it was no longer a broad church. “Antisemitism is rife and tolerated,” she said in her leaving speech. “Loyalty cannot be an end in itself.”

But she repeatedly refuses to criticise Jeremy Corbyn’s record on education, and finds the assumption that people are either completely rightwing or leftwing a “serious irritation”. You can be rightwing on some issues and leftwing on others, she explains. On Labour’s pledge to raise school funding, she says: “Of course we all agree that there should be an increase in funding for education, but what that increase should look like, where that increase should be invested, is less clear to me.”

In her leaving speech, she also spoke about her father’s passionate belief in education, and how, without Harold Wilson’s Labour government and his commitment to expand higher education, she would not have gained her degree in sociology from the Borough Polytechnic Institute in London (now London South Bank University), after attending grammar schools in Bodmin, Cornwall, and Bushey, Hertfordshire. Her mother, a nurse, was the daughter of a farm labourer, and her father, a flight engineer in the air force, came from a “very poor” family and was one of seven children. “He had a very brutal childhood,” she says. “I think it did leave me, as it left him, with the absolute belief that schools can be transformational for disadvantaged children – that, outside the family, schools can offer the only hope of their circumstances being mitigated and the mistakes of previous generations not being repeated.”

Her time as a social worker has affected her deeply. “I’s a very, very, very, very hard job ... completely heartbreaking.” Memories of seeing children who feel scared in their own home provide her with “a constant reminder of what life can be like if you’re a small child in that situation”. That’s why, she says, “I am very passionate about the extra safeguarding and support the schools are giving to children – and the need for them to be properly funded for it.”

So funding is important? “Clearly, the current funding formula is not working. Schools aren’t getting sufficient funding for what we’re asking them to do, plus the government is saying they’ve got more money than they used to have. Which may be right – but it doesn’t recognise the extra roles that schools are having to take on.”

Before the Independent Group spent any money on education, however, there would be clarity about what it was seeking to achieve. “I would not want change for change’s sake, but changes that will genuinely achieve the objective of giving opportunity to every child, and made on the basis of evidence of what will work and what won’t.”

It seems ironic, considering her group’s preferred new name, that Coffey is so cautious about change.