Scottish councils are to be hit with a second wave of industrial action as 150,000 employees prepare to walkout in an ongoing pay dispute. All three major public sector unions – Unison, Unite and the GMB – are to stage a 24-hour stoppage on September 24 after the Convention of Scottish Local Authorities (COSLA) refused to increase its pay offer for next year of 2.5%. Unison's Scotland Regional Officer and Secretary to the joint trade union negotiating team Dougie Black said: ‘Taking industrial action is regrettable but now unavoidable. ‘We have no alternative given the employers' behaviour over this.' Council workers walked out last month on August 20 in the same dispute. COSLA spokesman Cllr Michael Cook said: ‘The real cause of the impasse is that at our last meeting the unions simply reiterated their original demand of 5% or £1,000 on each spinal column point whichever is the greater. ‘In light of this stance by the unions, employers really had no alternative but to reaffirm their offer of 2.5%. ‘However, we modified it as a one-year offer of 2.5 % for 2008 – 2009. ‘To increase the offer beyond this level would mean service reduction and job losses – it is time for the unions to be a bit more realistic in their demands.'