Labour plans to increase the minimum wage could cost more grocery retail jobs than its proposed hike in national insurance, it has been claimed.

The main political parties released their manifestos this week, with Labour unveiling plans to pin increases to the minimum wage to average earnings over the next five years.

"While plans to increase national insurance by 1% will be a tax on jobs, the plans to hike the minimum wage could be an ever-bigger problem for retailers and could see them cutting jobs," said ACS public affairs director Shane Brennan.

BRC director general Stephen Robertson added: "The BRC supports the principle of the minimum wage but it must reflect economic realities and not hinder retailers' ability to maintain and create jobs. It should not increase faster than average earnings. That would disproportionately affect those people the youngest and oldest employees who find it most difficult to get jobs."

The Liberal Democrats pledged to set the minimum wage at the same level for all workers over 16.

Meanwhile, the Tories plan to double fines for retailers selling booze to under-18s and to give extra powers to local communities to shut stores that offend repeatedly. They also pledged to introduce a variable fuel duty to help stabilise prices and to lower corporation tax.

Both the Tories and the Lib Dems announced plans to ban the below-cost selling of alcohol, while Labour pledged not to introduce VAT on staple food. All three parties said they would press ahead with plans for a supermarket ombudsman, as the industry remained high on the agenda for campaigning politicians.

David Miliband held a surgery at an Asda in South Shields and Lib Dem leader Nick Clegg visited an Asda in Oldham on the day of his manifesto launch. Gordon Brown and David Cameron posted video messages to mums on Asda's website, while Cameron paid a visit to a Fuller's brewery in London.