Image copyright Reuters Image caption British Airways said reports of bed bugs were extremely rare (file photo)

British Airways has apologised to a Canadian family after they were bitten by bed bugs on an overnight flight.

Heather Szilagyi was flying from Vancouver to London with her eight-year-old daughter and fiancé earlier this month, CTV reported.

After spotting the bugs, Ms Szilagvi complained to the flight attendant but was told she could not change seats.

She said she and her daughter woke up the next morning covered in bug bites.

British Airways offered an apology to the family.

"We have been in touch with our customer to apologize and investigate further," an airline representative said in a statement.

"British Airways operates more than 280,000 flights every year, and reports of bed bugs on board are extremely rare.

"Nevertheless, we are vigilant and continually monitor our aircraft."

Ms Szilagvi said that as someone who has worked in the hotel industry, she easily spotted several on the seat in front of her during the flight.

She said she had alerted the flight attendant, but was told nothing could be done.

"She was like, 'Oh ok, sorry about that. We're sold out. We don't have anywhere to move you'," Ms Szilagyi told CTV Vancouver.

Once they landed, Ms Szilagvi said she and her daughter were covered in bug bites. She phoned customer service to alert them to the problem and to ask that they not be on the same plane going home.

After several attempts to get through to customer service failed, she posted pictures of the bites on Twitter.

The airline then reached out to apologise, and offered them an upgrade to business class for their flight home.

"We were not asking for a refund. All we were asking for was a flight on a different plane, to make sure it was a different plane, to make sure that the plane that was infested with bed bugs was taken care of," she told CTV.