Premier Inn, the budget hotel chain, is to invest £100m in developing six new hotels in London.

Whitbread, the company that owns the chain, has bought the Quality Hotel in Westminster, the Comfort Inn in Kensington and the Purple Hotel in the City for a total of £18.5m.

The hotels add for 400 rooms to the group’s portfolio and an additional £12m will be spent rebranding the sites.

Whitbread has also secured the first right of refusal to acquire the remaining 12 Purple Hotels from the Real Hotel Company should they come up for sale.

In addition to the acquired sites, three new hotels will be built in the Greater London area, in Waterloo, Ealing and Old Street, costing the company £70m. The three hotels, which will add 800 rooms, are scheduled to open by 2011.

Alan Parker, chief executive of Whitbread, said: “We have exciting expansion plans for Premier Inn in London and this addition of 1,200 rooms is a great start.

“The capital is an important focus for the company, and there is an increasing need for high-quality, affordable accommodation. Our further pipeline will position us as the largest hotel chain in London with at least 8,500 rooms before the 2012 Olympics.”