(ShareCast News) - Newspaper publisher Johnston Press swung to a loss in the first half, mainly on the back of an impairment charge.For the 26 weeks to 2 July, the company posted a statutory pre-tax loss of £183.7m versus a £2.2m profit the year before, as it booked a £183.6m non-cash impairment reflecting a change of assumptions on its publishing titles and print assets.Advertising revenues were down 17.9% in the first quarter but improved marginally, with a 15% drop in the second quarter despite the impact of the run-up to and uncertainty following the UK's vote to leave the European Union in June.Johnston Press said the acquisition of the i newspaper resulted in an increase in circulation revenue of 2.3% to £38.4m, with its performance offsetting declines in pre-existing titles.Chief executive Ashley Highfield said: "The acquisition of the i newspaper in April was transformational for Johnston Press. Since the acquisition we have increased circulation considerably, using the extensive JP distribution network, and continued to grow market share."The market continues to be challenging and uncertainty surrounding the outcome of the Brexit negotiations has caused further softness in some segments of the advertising market, in June and July. Nevertheless, we are focused on our strategy of increasing overall audiences, maximising opportunities for the i, maintaining tight cost control and rebalancing our portfolio. In that respect, we are nearing completion of the disposal of our Isle of Man newspaper group for £4.25m and are well advanced in negotiations for further divestments."At 0955 BST, shares were down 17% to 11.40p.