But Labour's industrial relations spokeswoman, Darien Fenton, said it was a model for growth based on "longer hours and lower wages".
Labour's policy, which was released last week, was effectively the opposite in seeking to strengthen collective bargaining and making standard conditions across private sector industries, where a reasonable level of collective bargaining already existed.
The conditions, to be called Industry Agreement Standards, would apply across the industry including to non-union workers.
Ms Fenton said scrapping the duty to conclude would be an invitation for employers to stall negotiations, eventually leading to strikes and a breakdown in employer-employee relations. She said ending the 30-day rule would invite employers to hire only those willing to sign individual agreements over those wanting to join collectives.
"It would undermine anything the unions do.
"A new worker coming into the job, they'll be forced to take the boss' agreement every time and then there'll be a body of workers no longer covered, which would undermine the collective agreement."
Ms Fenton said Mecas were common in the public sector, and an opt-out clause would see lower wages and conditions.
"So you get the ridiculous situation in the health sector where you've got one group of 20 contractors competing with another in the same hospital."
She said it was a return to the 1990s when the Employment Contracts Act crippled unions, though she saw the humour because Labour's policy was criticised by National as a throwback to the national awards of the 1970s.
Meanwhile, Mr Key announced a new youth wage, to be set at 80 per cent of the minimum wage and to apply for six months to workers aged 16 and 17, workers aged 18 and 19 coming off a benefit, or to 16- to 19-year-olds training in a recognised industry course.
It would replace the new entrants' wage, which is set at the same rate.