Two of the world’s biggest travel companies - Tripadvisor and Booking.com - have announced a strategic partnership that sees new battle lines drawn between the leading online brands.

Booking.com, which dominates the online travel business in Europe, has announced it will make its 436,000 hotel listings available to book directly through Tripadvisor after resisting collaborating with the site’s instant booking platform last year.

The move means Tripadvisor users will now be able to book more than 700,000 hotels directly, without having to click through to a third-party site.

User-generated review site Tripadvisor, which has 5.2 million listings for hotels, restaurants and other travel attractions around the world, launched an instant booking feature last year following increased competition between the brands.

This summer Google entered the travel market, launching its own direct booking service, while Airbnb is expected to steal a substantial amount of business from sites such as Booking.com as it continues to shake the foundations of the hospitality industry.

At first, booking sites such as Booking.com - owned by Priceline Group - and Expedia refused to join Tripadvisor’s instant bookings platform. The decision by Priceline to collaborate is a major shift. Other Priceline sites, Priceline.com and Agoda.com are likely to follow Booking.com.

“Having the Priceline Group join the instant booking platform is a huge win for travellers and we couldn’t be more thrilled to have them as our first strategic, global online travel agency partner,” said Stephen Kaufer, president and CEO of TripAdvisor said in a press statement.

Meanwhile Expedia has bolstered its ranks by taking over another major third-party travel booking site, Orbitz.