Staff are doing their best, Unison says

It also wants Education Secretary Ruth Kelly to employ more cooks, in an effort to supply healthier food.

Ms Kelly is due to outline her plans for training catering staff as part of a �280m school dinners overhaul.

But Shadow Education Secretary David Cameron said a "clear strategy", including a junk food ban, was needed.

'Limited resources'

Speaking at Unison's annual conference for school meals workers in London, Christian McAnea, the union's head of education services, said: "The staff have been doing their best with the resources and time available but we want them to be given the time to cook meals from scratch.

"This can only be done by increasing the hours they work and employing more people.

"The government's plans to invest more money into school meals is vital, but it will take more than just money to turn this around.

"We need to have a properly planned workforce that has access to training and follows a minimum set of national standards."

Ms Kelly is expected to tell the conference that school dinner workers are "unsung heroes".

Around 15,000 staff across England will take a course from next year, which includes how best to use fresh food.

Ms Kelly will say: "The new vocational qualification will recognise for the first time the crucial skills and experience that dinner ladies, school cooks and support staff bring to their work.

"It will ensure that everyone in the school kitchen aspires to the same high standards."

Ministers are giving �220m to schools and local education authorities for ingredients so at least 50p is spent on dinners for primary school pupils and 60p for secondary school children.

The School Food Trust, which is receiving �60 million, is looking at banning certain junk foods and studying how schools can get out of catering contracts.