LONDON (BLOOMBERG)- Royal Bank of Scotland Group will close 259 more branches across Britain in its latest round of cuts as customers shift to online banking.

Outlets under both the NatWest and Royal Bank of Scotland brands will close in the middle of next year, resulting in about 680 job cuts, the company said on Friday (Dec 1). RBS said it will use the savings to invest in its smartphone offering, which has seen mobile transactions rise more than 70 per cent since 2014.

RBS, which says 5 million customers use its mobile app, has been shrinking for almost a decade since it was nationalised. It announced 690 job cuts and 180 branch closures in March. Its competitors are moving customers online too, with Lloyds Banking Group announcing it will shut 49 branches next year.

Unite, Britain's largest labour union, criticised the move, saying it will cause 1,000 job losses and may spell the end of bank branches in the country.

"This British-taxpayer funded bank should be concentrating on investing in jobs here in the UK, rather than cutting them wholesale," Unite national officer Rob MacGregor said in a statement on Friday.

"Why is the government signing off this alarming branch closure programme?"