McDonald's, the global fast food brand, is to undertake a major investment and refurbishment programme at its Scottish outlets that will also see its franchise base extended, and an increase in orders for its local suppliers.

The chain, which operates 93 outlets and employs 3500 staff in Scotland, intends to spend £2m on the programme, to be backed up by a media campaign designed to counter the recent raft of adverse publicity to hit its brand.

Steve Easterbrook, UK chief executive, speaking yesterday during a visit to one of its main Scottish suppliers, delivered a robust defence of his chain's sense of corporate responsibility in the wake of Prince Charles' call for the "Big Mac" to be banned, and politicians laying the blame for child obesity squarely at its door.

He declined to answer directly the prince's comments, describing them only as, "very disappointing - if true".

However, he added: "It is our intention to address robustly the gap between people's perceptions about us. Recent comments show that perception in many cases is sadly out of date."

The chain has a significant presence in Scotland, and the new programme is aimed at increasing it. At present, 38 of the Scottish outlets are owned by 15 franchisees. Easterbrook said his aim was to grow the number of franchises to 50% of its total over the year, and then to 70% in later years.

The workforce is to increase to 5000, and as the average 7000 customers per week, per outlet is improved, the chain hopes for a substantial rise in its £100m-a-year turnover north of the border.

Speaking at one of McDonald's two main Scottish beef suppliers, Scotbeef at Bridge of Allan, Easterbrook said: "Growing the franchise component is crucial to our future. It requires a tremendous commitment on the part of the franchisee - 20 years. But that is what we are about. A global company, but managed locally. That is why we source our produce locally."

McDonald's takes the beef from 41,000 cattle a year from Scotbeef - 50% of its output - under a contract worth £10.9m a year. And in all, the fast food chain buys up 10% of Scotland's entire beef output.

Ian Galloway, chairman of Scotbeef, said McDonald's contract was key to the company's £110m-a-year turnover. He said: "We have a long and cordial relationship with McDonald's lasting over 15 years, and look forward to growing our business over the coming year."

McDonald's growth is to be driven by a new message. Easterbrook said: "There is an obesity problem in this country. But it is wrong to say we are part of it. It is for government to set targets to reduce obesity, and it is for us to see what part we can play to help achieve those targets.

"And we feel we have a very positive role to play in influencing a child's diet. Already 60% of the items on our menus are new, in the past three years. We have reduced salt in our burgers and buns by 30%. The fat and salt in fries by 20%. We have introduced a whole new range of drinks from mineral water to fruit juices and sugar-free drinks. We now make sure customers have all the nutritional information they need on our packaging."

He said the company is equally aware of the litter issue around its restaurants and is working with local authorities to demonstrate to residents and businesses that operate near McDonald's restaurants the chain's commitment to clean streets.

There has been a significant reduction in packaging, the chain has instigated a "Just Bin It" campaign, and local managers are required to draw up "litter travel paths" and "hotspots" that staff police twice a day.

The chain is also working to improve its working conditions, and has turned the dismissive "McJob" slur against its detractors.

An ad campaign is now running, asking prospective employees to check out the "McPay", "McCareers" and "McFlexibility", which it says are all, "Not bad for a McJob".

Easterbrook added: "McDonald's is very particular about the people we employ. We turn down three for every one we hire. Last year we had an all-time low for staff turnover so that now the average hourly paid member of our team has been with us for two years.

"Our selection techniques are very specific, and once we hire, we like to keep. We run comprehensive training schemes, and have definite career paths for our workforce. Half our senior management team, 80% of restaurant managers and one in five of our franchisees all started as hourly-paid workers."

Last August, the company launched a dedicated online learning programme open to all its 67,000 UK workers. Designed in conjunction with the Learning and Skills Council, the programme offers GCSE-level qualifications in literacy and numeracy, run by the Cambridge Examination Board. So far, more than 1000 staff members have been through the courses.