Royal Bank of Scotland highlighted the challenges facing its new chief executive Alison Rose today.

A weak performance at its investment bank NatWest Markets and yet another mis-selling charge tipped it into a third-quarter loss.

RBS, which owns Ulster Bank here, reported an £8m pre-tax loss in the three months to the end of September, compared to a £961m profit for the same time last year. 

Alison Rose is due to head a new-look management team from next month at RBS, which made a fresh £900m provision to compensate customers who were mis-sold payment protection insurance (PPI) on loans and credit cards. 

UK banks were stung by a late surge in PPI queries ahead of an August claims deadline, sending the industry's final compensation bill above £43 billion. 

"It would be a very brave FD (financial director) who said the line was completely drawn under it," RBS chief financial officer Katie Murray told reporters. 

The charge was at the top of a £600-900m range forecast by RBS in September and knocked the bank's core capital ratio by 50 basis points to 15.7%. 

Ms Rose will have to tackle its investment banking arm, which posted a loss of £193m, with total income dropping by £419m to £150m compared with a year ago.

Joe Dickerson, analyst at Jefferies, said the performance of NatWest Markets was "deplorable" and Rose would come under pressure to further restructure the overall business. 

RBS said the unit suffered heavily during August and September, when borrowing costs in US overnight lending markets soared and investors grappled with global recession signals, trade tensions and the threat of a chaotic Brexit.

Murray said she could not rule out further restructuring of the business, but wider cuts would be a decision for Rose.

Alison Rose, an RBS veteran who will become the first woman to lead one of Britain's big four banks, will outline her new strategy in February.

Alison Rose, an RBS veteran, will become the first woman to lead one of the UK's big four banks

She inherits a smaller bank that returned to profit and paying a dividend under predecessor Ross McEwan, who will become CEO of National Australia Bank in December. 

Big challenges facing Rose include accelerating the return of the majority state-owned bank to private hands and stepping up distributions of excess capital to investors. 

Shareholders have called on RBS to radically pare back its investment banking activities to concentrate on higher-returning businesses. 

While mortgage lending grew to £8.6 billion in the quarter, up from £6.7 billion three months earlier, RBS blamed intensifying competition for squeezing its net interest margin by 5 basis points to 1.97%. 

RBS had in August ditched its profitability and cost targets for next year due and Murray said business borrowers were continuing to delay investment decisions. 

The bank posted £213m of impairments for the quarter, above expectations. 

Investor sentiment towards Britain's lenders has recently improved as the chances of a disorderly Brexit have receded, boosting bank share prices including RBS by around 15% for the year to date.