Profits at coffee shop chain Costa have risen by a fifth after more strong sales and a surge in the size of its UK estate to more than 1,600 stores.

The retailer, which is part of the Whitbread leisure group, grew total worldwide sales by 19.5% to £569.2million in the six months to August 29, while underlying profits were 20.5% higher at £43.5m.

It added a net 86 stores in the UK, meaning its estate of 1,664 outlets in locations ranging from high streets and shopping centres to motorway service areas and garage forecourts is now 800 greater than its closest competitor.

The chain also recently marked the milestone of 1,000 international stores with a new outlet in Bangkok.

Costa’s continued strong growth combined with further market share gains at budget hotel Premier Inn to help Whitbread post a rise in half-year underlying profits of 12.6% to £216.1m.

Premier improved like-for-like sales by 3.3% and added 1,368 UK rooms, taking its total to 53,039. Revenues grew by 12.2% to £497.4m.

Across the group, Whitbread said it created 1,200 new UK jobs over the period, with a further 10,000 expected in the next three years.

In April 2011, the company pledged to grow the number of Premier Inn rooms in the UK by around 50% to 65,000 by 2016. It extended the target in April to 75,000 by 2018.

The company expects to open around 4,000 new Premier Inn rooms in the current financial year and a further 4,500 in 2014/15.

Chief executive Andy Harrison said: “This good first half performance puts us on track to deliver this year’s business plan and we remain on the right trajectory for our 2016 and 2018 growth milestones.”