A two-week-long lock-out by the Progressive supermarket chain is starting to make itself felt in Northland, with shelves starting to empty of some goods and a union picket in Whangarei on Saturday. Police were called around noon when picketers briefly prevented a truck entering Okara Countdown. Organisers claimed two trucks hadvoluntarily turned away earlier in the day. About a dozen union representatives took part in Saturday's picket, which they said aimed to boost public support and counter "disinformation" from the company. National Distribution Union Northland organiser Trevor Noel said posters in the supermarket windows claimed the workers were on strike, when they had in fact been locked out. Australian-owned Progressive - which owns Countdown, Woolworths and Foodtown supermarkets - was "an out-and-out clobber machine for Kiwi workers," Mr Noel said. The dispute centres on demands by the National Distribution and Engineering, Printing and Manufacturing unions for a national agreement covering workers at Progressive's distribution centres in Auckland, Palmerston North and Christchurch. At present Palmerston North workers earn $1.50-$2.50 an hour more than their Christchurch co-workers, with Auckland rates halfway between. About 600 distribution workers initially went out on a two-day strike, but have been locked out until they agree to return under the company's terms. Progressive says a national collective agreement is non-negotiable and would hit customers by driving up costs. Supermarket workers will apply for mediation today as the lock-out of distribution workers continues. National Distribution Union southern secretary Paul Watson said an application for mediation would be lodged today but it was not yet known when talks would happen.