1XL is designed to harness the aggregated strength and scale of local media to give advertisers "unprecedented UK-wide digital reach".
The media companies claims the partnership could "revolutionise local media buying", providing reach of more than 17.5 million monthly unique users across a combined portfolio of more than 800 sites.
The 1XL platform, which officially launches today (19 November), will be run through a dedicated media sales team at national sales house Mediaforce Group.
The collective claims to be larger than any single commercial UK national news media website and similar in scale to digital advertising platforms AOL and MSN.
The platform will draw on data from each publisher and third party data, alongside semantic and contextual targeting capabilities, to optimise audience targeting and maximise performance of advertising campaigns.
It will also enable ads to be served around the most relevant and engaging content, and will be underpinned by leading geo-demographic analysis and insight provided by Mediaforce Group.
Ashley Highfield, chief executive of Johnston Press, said: "The 1XL collaboration gives advertisers and their agencies, for the first time, the ability to scale their campaigns through ‘mass localisation’, and, as such, it is a monumental step forward for local media publishers, and we’re delighted to be partnering with Local World, Newsquest and the independents to help deliver this."
Henry Faure Walker, chief executive of Newsquest, said: "Online display advertising is now worth over £2 billion per annum, a market hitherto dominated by the likes of Google and Facebook. We look forward to local news publishers, with the huge investment they make in quality content and local journalism, being able to take their rightful share."
Blanche Sainsbury, commercial director at Local World, said: "It is clear from feedback in the market that there is strong demand for taking national brands local. Providing advertisers with access to our combined online portfolio shows how 1XL is a compelling option for reaching the UK consumer in a trusted and engaging environment."
*Image from Carat