John Lewis is preparing to unveil the biggest store revamp in its history as it fights back against turbulent high street trading.

The September overhaul will include the opening of rooftop bars and pop-up cinemas, as well as its biggest ever investment in private-label fashion.

John Lewis said it is turning 15 of its existing shops into “pilot stores” where it will test the ideas, alongside personal stylists, events and classes.

John Lewis is pressing ahead with the radical revamp after its parent company, John Lewis Partnership, warned profits would be “close to zero” in the first half of its current financial year.

At an update last month in which it mapped out its vision for the next decade, the Partnership said its strategy would focus on differentiation rather than scale, investing heavily and placing partners at the heart of its business.

As revealed by Retail Week, its two businesses will rebrand to John Lewis & Partners and Waitrose & Partners.

Paula Nickolds, managing director of John Lewis, told The Daily Mail: “It’s a really, really tough time for retail at the moment, and I think that was clear at the strategy update we made last month.”

As part of the overhaul, John Lewis will carry out a “multi-million pound” refurbishment of the womenswear floor at its Oxford Street flagship and install a new shoe room in partnership with Kurt Geiger.

The Oxford Street store will also host a cinema in its rooftop bar. And John Lewis is considering opening a similar space on the roof of its Southampton store – one of its pilot shops.

Nickolds added: “At a time when other retailers might be cutting back, I am determined that we will invest in differentiation and innovation to ensure we take advantage of our unique position.”

As previously reported, John Lewis is making its biggest-ever investment in fashion, launching a new range of 800 womenswear product, as it bids to ramp up its own-label credentials.

The retailer wants 50% of its sales to come from private-label lines by 2020.