Image caption The Department of Health says cutting the amount of saturated fat in people's diets could save lives

A pledge by food manufacturers to cut saturated fat levels is "a drop in the ocean" in the fight against obesity, a top public health expert has said.

Morrisons, Subway and Nestle are among firms signed up to the voluntary "responsibility deal" between industry and government.

But Prof John Ashton, president of the Faculty of Public Health, said the approach "lacked credibility".

The Department of Health (DoH) said it would "make a huge difference".

It says the average man should eat no more than 30g of saturated fat a day, while the average woman should eat no more than 20g.

According to the British Dietetic Association, most people eat about 20% more than the recommended maximum levels - and a survey of 2,000 people for Sainsbury's found 84% of those questioned did not know how much saturated fat was a healthy amount.

'Healthy options'

Media playback is unsupported on your device Media caption Public health minister for England Jane Ellison says more than 500 big companies have pledged their support

The DoH said cutting the amount of saturated fat in people's diets by 15% could prevent around 2,600 premature deaths every year from conditions such as heart disease and stroke.

Almost half of the food manufacturing and retail industry - based on market share - has signed up to this latest pledge to reduce the amount of saturated fat in products, the DoH said.

Measures planned by companies include Nestle altering the make-up of KitKat biscuits, Morrisons reformulating its range of spreads and Subway replacing biscuits and crisps in its Kids' Pak with healthier options.

Other firms which are cutting saturated fat or have pledged to do so include Tesco, Sainsbury's, Aldi and Mondelez International - which will alter products including its Oreo biscuits.

Prof Ashton said that, while it was "a good thing that some companies are making food that has less saturated fat than before", the pledge did not go far enough.

Saturated fat Image caption Most people eat 20% more than recommended levels, the British Dietetic Association says Saturated fat is the kind of fat found in butter and lard, pies, cakes and biscuits, fatty cuts of meat, sausages and bacon, and cheese and cream

Eating a diet that is high in saturated fat can raise the level of cholesterol in the blood, which increases the risk of heart disease, according to NHS Choices

Most of us eat too much saturated fat - about 20% more than the recommended maximum amount

The average man should eat no more than 30g of saturated fat a day

The average woman should eat no more than 20g of saturated fat a day

"They need to ensure that at the same time they lower the sugar and salt that they have used to make foods more tasty as a result of lowering the fat content."

He added: "This announcement is a drop in the ocean in comparison with the scale of the obesity crisis.

"We cannot rely on the voluntary approach of the responsibility deal to solve this problem.

"It now lacks credibility and can be seen as a feeble attempt by the industry to save face."

Labour public health spokeswoman Luciana Berger said: "A few company names on a non-binding plan with no timescale stands little chance of delivering the fundamental change needed to improve our national diet.

"In the week that the chief medical officer warned of the long-term dangers of childhood obesity, we need to go much further."

She said Labour had put forward "bold ideas to set legal limits on our food's fat, sugar and salt content and achieve a cross-party ambition for a more physically-active nation".

'Huge progress'

Tam Fry of the National Obesity Forum, also called for regulation, adding: "The much-vaunted voluntary responsibility deal will never succeed until the government takes a grip and makes everybody sign up to it."

Media playback is unsupported on your device Media caption Prof Alan Maryon-Davis of the Faculty of Health is concerned little is being done

The DoH said that "by reducing the amount of saturated fat in everyday foods, manufacturers and retailers are helping us lead healthier lives".

"We have already made huge progress through the responsibility deal - there are reduced salt levels in many products, calories on high street menus and better information about alcohol units and drinking guidelines," a spokesperson said.

"We know there is more to be done but today's pledge will make a huge difference to our health."

Prof Susan Jebb, chairwoman of the Responsibility Deal Food Network, said the manufacturers' commitments to help reduce saturated fat were "an important step forward".

The announcement of the pledge comes days after cardiologist Aseem Malhotra, a member of the Academy of Medical Royal Colleges' obesity steering group, wrote in the British Medical Journal that the risk from saturated fat in non-processed food was "overstated and demonised".

He said there was too much focus on the fat with other factors such as sugar often overlooked.

He told Radio 4's Today on Saturday that "a sugary drinks tax, banning junk food advertising to children, ensuring compulsory nutritional standards in schools and hospitals... are things that are going to overcome the problems that we face".