These results are weaker than analysts had hoped for, with Costa achieving just 3.0 per cent like-for-like growth in the 11 weeks to 15 August.
Whitbread said that Costa performance was biased towards the first quarter "due to the colder weather in the first quarter and warmer weather in the second quarter."
In London, the Premier Inn hotel chain saw total sales grow by 16.1 per cent in the quarter, as room numbers increased by 11.9 per cent in the year to date.
That compares with national growth of 10.4 per cent, showing the regional divide between the London economy and the rest of the UK.
Whitbread has opened 78 net new Costa Coffee stores in the UK in the year to date, and are on track to open 300 net new stores and 850 Costa Express units in the full year.
Andy Harrison, chief executive of Whitbread, said:
Whitbread delivered another good performance, with total sales growth of 10.8% for the 11 weeks to 15th August and like for like sales growth of 2.1%.
So far this year Premier Inn has grown total sales by 12.1%, like for like sales by 2.9% and added 1,270 new rooms, with especially strong growth in London, where total sales were up 17.7%.