Sir Stuart Rose has defended M&S against claims that the high street chain's carrier bag charges are a publicity stunt.
The M&S chief executive said the green initiative had been ridiculed by critics but he added that the vast majority of his customers had taken well to paying for the plastic bags.
"We have had 150 complaints out of six million transactions and our customers have got it," said Sir Stuart, speaking at the British Retail Consortium (BRC) conference in London last week.
He added that paying for carrier bags is not the only solution to tackling climate change alone, but it is a promising start.
M&S started charging 5p for the bags nationwide in May after trialling the initiative at 50 stores in Northern Ireland and the south west. It donates the profits from the charge to environmental charity Groundwork.
Supermarkets in the UK give out around 13bn plastic bags every year and some take up to 1,000 years to decay.