Guardian News and Media is tipped to report a multi-million pound loss in its next set of results as rampant web traffic has failed to translate into commercial success.

According to sources, cited by The Telegraph newspaper, the left-leaning group will reveal how it has not managed to get a foothold in the US advertising market, despite having one of the largest online readerships in the world.

"The Guardian still hasn't got to grips with American media sales," said a source to The Telegraph.

"The New York [advertising] market is a difficult place to break into. Selling advertising is not the same as building a website. People and relationships are important."

GNM has spent tens of millions of pounds over the last six years to forge a US website geared towards left-leaning Americans.

On average, it receives around 85 million monthly browsers and over 4.5 million unique users a during the same period.

In 2013, GNM, the publisher of The Guardian, The Observer and three versions of Guardian.com, reported a pre-tax loss of £40.5m (€50.8m, $60.4m) although the overall group reported a pre-tax profit of £22.7m.