Ministers have warned the food industry to "get serious" about reducing the salt content in popular products.

The Times revealed on Thursday that health ministers had written to major companies warning them that the salt content in some processed foods was still too high.

The pressure comes as the government steps up its drive to combat heart disease.

A letter to major companies seen by the paper warned company bosses that the voluntary approach to dealing with the issue was failing.

It said that plans put forward by the companies would cut salt intake by only 0.6 grams per day by 2005.

That compares to the government's target reduction of six grams per day

"What is needed are real commitments for key product categories such as pizza, breakfast cereals, sandwiches and ready-made meals to ensure that we reach the necessary reduction in salt intakes from processed foods," public health minister Melanie Johnson wrote.

Stepping up the pressure, a source "close to" health secretary John Reid told the Times: "This period of time is an opportunity for companies to show that they are serious.

"Labour governments have regulated in a tough manner before — look at the ban on tobacco advertising. That is what happens if industries do not get serious."

However, the companies involved have insisted they are making progress in reducing the salt content of key foods.