Tesco-backed coffee chain Harris + Hoole suffered a doubling of its pre-tax losses last year as it invested in its store expansion.

The artisan-style coffee shop business opened 22 new shops in the 52 weeks to March 1, taking its year-end total to 45.

But that resulted in its pre-tax losses rocketing almost 100% from £12.8m to £25.6m, according to documents filed at Companies House.

Sales increased to £12.8m from £6.6m the previous year as a result of the additional store space. But the cost of sales rose to £19.5m, dwarfing those revenues.

The filing revealed that Harris + Hoole will require a further £6m of further funding from Tesco until the end of 2017 in order to meet its financial targets.

The supermarket giant, which owns 49% of the coffee chain, has already committed to plough up to £7.5m into the business over a 12-month period.

A spokeswoman for Harris + Hoole said: “These results cover the period ending March 1 this year and clearly reflect a challenging trading period for us – but since these results were filed we’ve seen encouraging trends in our like-for-like trading.

“We’ve also put in place a series of measures to stabilise and consolidate the operating model of the business. As a result, we have solid foundations to support our long term ambitions to become the high street leader in quality coffee.”

Retail Week revealed in July that Harris + Hoole founders Nick, Andrew and Laura Tolley were stepping down from the business to concentrate on expanding their other chain, Taylor Street Baristas.

However, it is understood the siblings retained their stakes in Harris + Hoole, totalling 51% between them.