McDonald's has apologised to a mum who claimed to have found a piece of metal that "looked like a bullet" in her son's Big Mac.

Lindsey Gladdish visited the Thamesmead branch of the fast-food chain late on Friday evening to pick up some dinner for her 11-year-old son.

However, she said that when she opened up the burger to take out the lettuce, she found a scrap of metal wedged inside the meat of the patty.

"Thank God I checked it first. He could have choked on it or swallowed it and it would have been awful," Lindsey told News Shopper.

Lindsey took the burger straight back to McDonald's to demand an explanation.

She said: "The manager took the burger off me and he said it looked like the metal was already in the meat. He said it needed to be sent off for further examination."

Lindsey then went back home and was told someone from McDonald's would be in touch.

She said the next day she received a phone call from staff at the restaurant, who explained the metal had most likely fallen off one of the grills in the kitchen. They then offered her vouchers for two free meals at McDonald's.

"I doubt I'll be using them," Linsey told News Shopper.

"It's put me off to be honest with you. It's something that shouldn't have happened.

"Thousands of people a week get their food from there. It's ridiculous.

"If it had been in a Happy Meal, a baby could have eaten it and choked."

A spokesman from McDonald's apologised for the incident and confirmed the burger patty will be sent off for testing.

He said: "We are sorry to hear about this customer’s experience. Food safety is of the utmost importance to us and we place great emphasis on quality control, following rigorous standards to avoid any imperfections.

"As soon as this matter was brought to our attention, we apologised and started an investigation."