Whitbread has posted an 8.6% rise in sales for the third quarter as underlying business at its Costa Coffee chain strengthened but weakness at its Premier Inn hotel business in London weighed. 

Whitbread, Britain's biggest hotel and coffee shop operator, said like-for-like sales at Costa grew 4.3% in the 13 weeks to December 1.

This was up from a 2% rise in the 13 weeks to September 1. 

However, Whitbread reported total revenue per available room, the hotel industry's preferred measure for its London hotels fell 6% for the third quarter.

The company's chief executive Alison Brittain reassured investors that annual figures should meet forecasts. 

"Trading since the end of the quarter is such that we expect to deliver full year results in line with expectations," she said. 

Whitbread said total sales at Premier Inn rose 9.2% for 13 weeks to December 1, with sales for 39 weeks to December 1 up 9%.

The company has opened 15 hotels in Britain since the start of the year, increasing the number of rooms available by 9.7%.