Illustration: Matt Golding. The commission's analysis is also humiliating for the SDA. It confirms the union negotiated a deal that in many cases appears to pay well below the award, the basic wages safety net. Commissioner Geoff Bull has proposed a series of undertakings be made by Coles to allow the workplace deal – one of the largest in Australia – to be approved. The undertakings would require Coles to pay higher rates for young workers, and much higher casual loadings, boosting the pay of tens of thousands of workers. They would also give Coles' workers a right to back-pay if they are worse off under the agreement. 'Sell out' of workers

Graham Smith, federal secretary of the Australasian Meat Industry Employees Union, accused the SDA of dudding workers, including meat workers. "This has been a sell-out of the members and this has vindicated our position on that," he said. "It comes down to a question of principles. Either you're going to operate as a union or you're not. [The SDA] has always been a big, heavy player in the ALP. I think they spend way too much time playing in that field and nowhere near enough time looking after members." The SDA is Australia's largest private-sector union and is well known for its strong stance within Labor on social issues, such as opposing same-sex marriage. A recent Fairfax Media investigation found the SDA pays major retailers, including Coles and Woolworths, up to $5 million a year in commissions for payroll deductions

In an email to Coles seen by Fairfax Media, Mr Bull noted a number of problems with the agreement, including lower penalty rates paid on weekends, loadings paid to casuals, and the wage rates paid to 17- and 18-year-old workers. He modelled the agreement against Coles' rosters to show that under the deal, some workers would be nearly 9 per cent worse off than the award. It is unlawful to pay under the award. The work by Mr Bull endorses a separate analysis of the deal by senior union official Josh Cullinan from the National Tertiary Education Union, first reported by Fairfax Media. Proposed changes will cost tens of millions Mr Cullinan, who did his analysis in a personal capacity, said the proposed changes by Mr Bull would cost Coles tens of millions of dollars.

He said a conservative estimate, based on limited publicly available information, would indicated the three undertakings proposed by Fair Work would cost Coles as much as $50 million a year. The undertakings would affect large portions of the Coles workforce and the changes to casual loadings proposed by Fair Work – which affect about 27,000 Coles workers – would probably add $15 million a year to its wage bill. The right for workers to have their wage compared to the award and to then receive back-pay would involve potentially much higher costs to Coles, Mr Cullinan said. Mr Cullinan's analysis found almost all 17-year-old workers and many 18-year-olds would be worse off under the agreement. Many adult workers who work more than half their hours on a weekend or week night would also be worse off, he found. The agreement provides for only a 20 per cent loading for casual staff, compared with 25 per cent under the award, as well as significantly lower weekend penalty rates.

SDA confirms commission has identified problems SDA national secretary Gerard Dwyer confirmed that the commission had identified problems with the agreement. "This is a comprehensive and detailed agreement, and we will work with the commission and the company to address the 17-year-old anomaly." Mr Dwyer said that the overwhelming majority of the 77,500 workers covered by the agreement would be "substantially" better off. He rejected any suggestion that the agreement was not in the interests of his members at Coles. He said the SDA had already begun talks with Coles to review sections of the agreement identified by the commission.

A spokesperson for Coles said: "Coles team members voted overwhelmingly in favour of the new three-year enterprise agreement. The Fair Work Commission is required to review all agreements. In Coles' case, they have sought further information and we are in the process of providing this to them." Mr Smith said if Coles didn't agree to the undertakings proposed by the Fair Work Commission, the whole agreement should be ripped up and negotiations started again. "There is no way you can convince us that Coles didn't know that this was going to give them a benefit that was better than the award," he said. He said the deal undercut the award by "significant amounts of money".