Costa Coffee has delivered an "outstanding performance", with underlying profits up 30% to £36.1 million, helping owner Whitbread to pre-tax profits of £191.9m.

The impressive run by Costa has resulted in 42 consecutive quarters of growth for the coffee chain.

Costa's successes have been helped by Costa Enterprises continuing to perform well; The chain added a further 794 new Costa Express units in the first half taking the total number of units to 1,986.

The conversion of petrol station Shell's Coffee Nation machines to Costa Express machines alone has resulted in cups sold per machine increasing by 20%.

International growth has also assisted - particularly in China, where strong growth delivered a like-for-like sales increase of 19.2%.

Premier Inn, another brand owned by Whitbread, also performed well, overcoming a decline in the wider hotel chain market to post a growth of 2.4% in revenue per available room.

Another 1,500 rooms were added by Premier Inn during the period, taking its total to 49.020, and it has plans to take extend this figure to 65,000 rooms by 2016.

Whitbread employs more than 40,000 people at 2,500 sites in the UK. In total, excluding one-off costs the underlying profits were up 10.6% to £193.4m, with total revenues up 14.2% to £1.02 billion.

Whitbread's chief executive Andy Harrison said in a statement that despite predictions of a flat consumer market, he expected to continue to outperform his competitors.

"We expect continuing rapid growth in total sales on track towards our five year milestones. Premier Inn is benefitting from a structural shift in the UK towards strong branded hotels. Costa's growth is supported by its leading UK position in a robust category, together with exciting international opportunities," he said.

"This growth in total sales, coupled with our clear focus on good financial returns, is creating substantial value."

Whitbread's restaurants, which operates the Beefeater and Brewers Fayre brands, also saw a slight increase in sales; total sales rose 5.3%, and like-for-like sales were up 3.4%.