(ShareCast News) - Shares in community news firm Johnston Press tumbled on Tuesday after the company issued a profit warning.The company said it expects first-half profits to be marginally below last year, impacted by a slowdown in general trading and specific weakness in the run-up to and after the election.The newspaper firm said in the 26 weeks to 4 July 2015 revenue was expected to fall by 5% year-on-year, while circulation revenues were expected to fall by 5.5% during the same period.Johnson Press said management took action to mitigate most of the revenue reduction in the period which limited the impact on profits on the period.Chief executive Ashley Highfields said trading conditions in the first half of the year were challenging."Whilst we expect this will have an impact on profit both at the half year and the full year, there are positive indicators coming through with digital growth and continued strong cash flow," Highfields said in a statement.Numis moved its rating for the company from 'hold' to ''under review' after the profit warning.It said the trading update was "disappointing" and adjusted its 2015 operating profit expectation from £55.9m to less than £51m, adding that it now expects earnings per share of 23p, compared with an earlier estimate of 23p.Panmure retained a 'buy' rating on the stock and cut its target price from 260p to 230p.Analyst Jonathan Helliwell said the update was not a total surprise, and noted the digital side of the company was progressing well."This update highlights one of the key risks in the stock, namely the continuing structural pressure and low visibility on print advertising - even in a sound UK economy," he said in a note.At 13:41, shares were down 17.2% at 117.62p.